stmhal: L4: Add support for external interrupts/events.

The L4 MCU supports 40 Events/IRQs lines of the type configurable and
direct.  But this L4 port only supports configurable line types which are
already supported by uPy.  For details see page 330 of RM0351, Rev 1.

The USB_FS_WAKUP event is a direct type and there is no support for it.

stmhal/extint.c

@@ -90,8 +90,16 @@
 // register in an atomic fashion by using bitband addressing.
 #define EXTI_MODE_BB(mode, line) (*(__IO uint32_t *)(PERIPH_BB_BASE + ((EXTI_OFFSET + (mode)) * 32) + ((line) * 4)))
 
+#if defined(MCU_SERIES_L4)
+// The L4 MCU supports 40 Events/IRQs lines of the type configurable and direct.
+// Here we only support configurable line types.  Details, see page 330 of RM0351, Rev 1.
+// The USB_FS_WAKUP event is a direct type and there is no support for it.
+#define EXTI_Mode_Interrupt offsetof(EXTI_TypeDef, IMR1)
+#define EXTI_Mode_Event     offsetof(EXTI_TypeDef, EMR1)
+#else
 #define EXTI_Mode_Interrupt offsetof(EXTI_TypeDef, IMR)
 #define EXTI_Mode_Event     offsetof(EXTI_TypeDef, EMR)
+#endif
 
 #define EXTI_SWIER_BB(line) (*(__IO uint32_t *)(PERIPH_BB_BASE + ((EXTI_OFFSET + offsetof(EXTI_TypeDef, SWIER)) * 32) + ((line) * 4)))
 
@@ -108,13 +116,26 @@ STATIC uint32_t pyb_extint_mode[EXTI_NUM_VECTORS];
 #if !defined(OTG_HS_WKUP_IRQn)
 #define OTG_HS_WKUP_IRQn 76  // Some MCUs don't have HS, but we want a value to put in our table
 #endif
+#if !defined(OTG_FS_WKUP_IRQn)
+#define OTG_FS_WKUP_IRQn 42  // Some MCUs don't have FS IRQ, but we want a value to put in our table
+#endif
 
 STATIC const uint8_t nvic_irq_channel[EXTI_NUM_VECTORS] = {
     EXTI0_IRQn,     EXTI1_IRQn,     EXTI2_IRQn,     EXTI3_IRQn,     EXTI4_IRQn,
     EXTI9_5_IRQn,   EXTI9_5_IRQn,   EXTI9_5_IRQn,   EXTI9_5_IRQn,   EXTI9_5_IRQn,
     EXTI15_10_IRQn, EXTI15_10_IRQn, EXTI15_10_IRQn, EXTI15_10_IRQn, EXTI15_10_IRQn,
-    EXTI15_10_IRQn, PVD_IRQn,       RTC_Alarm_IRQn, OTG_FS_WKUP_IRQn, ETH_WKUP_IRQn,
-    OTG_HS_WKUP_IRQn, TAMP_STAMP_IRQn, RTC_WKUP_IRQn
+    EXTI15_10_IRQn,
+    #if defined(MCU_SERIES_L4)
+    PVD_PVM_IRQn,
+    #else
+    PVD_IRQn,
+    #endif
+    RTC_Alarm_IRQn,
+    OTG_FS_WKUP_IRQn,
+    ETH_WKUP_IRQn,
+    OTG_HS_WKUP_IRQn,
+    TAMP_STAMP_IRQn,
+    RTC_WKUP_IRQn,
 };
 
 // Set override_callback_obj to true if you want to unconditionally set the
@@ -230,7 +251,11 @@ void extint_swint(uint line) {
     if (line >= EXTI_NUM_VECTORS) {
         return;
     }
+#if defined(MCU_SERIES_L4)
+    EXTI->SWIER1 = (1 << line);
+#else
     EXTI->SWIER = (1 << line);
+#endif
 }
 
 /// \method line()
@@ -273,12 +298,27 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(extint_obj_swint_obj,  extint_obj_swint);
 /// \classmethod regs()
 /// Dump the values of the EXTI registers.
 STATIC mp_obj_t extint_regs(void) {
+    #if defined(MCU_SERIES_L4)
+    printf("EXTI_IMR1   %08lx\n", EXTI->IMR1);
+    printf("EXTI_IMR2   %08lx\n", EXTI->IMR2);
+    printf("EXTI_EMR1   %08lx\n", EXTI->EMR1);
+    printf("EXTI_EMR2   %08lx\n", EXTI->EMR2);
+    printf("EXTI_RTSR1  %08lx\n", EXTI->RTSR1);
+    printf("EXTI_RTSR2  %08lx\n", EXTI->RTSR2);
+    printf("EXTI_FTSR1  %08lx\n", EXTI->FTSR1);
+    printf("EXTI_FTSR2  %08lx\n", EXTI->FTSR2);
+    printf("EXTI_SWIER1 %08lx\n", EXTI->SWIER1);
+    printf("EXTI_SWIER2 %08lx\n", EXTI->SWIER2);
+    printf("EXTI_PR1    %08lx\n", EXTI->PR1);
+    printf("EXTI_PR2    %08lx\n", EXTI->PR2);
+    #else
     printf("EXTI_IMR   %08lx\n", EXTI->IMR);
     printf("EXTI_EMR   %08lx\n", EXTI->EMR);
     printf("EXTI_RTSR  %08lx\n", EXTI->RTSR);
     printf("EXTI_FTSR  %08lx\n", EXTI->FTSR);
     printf("EXTI_SWIER %08lx\n", EXTI->SWIER);
     printf("EXTI_PR    %08lx\n", EXTI->PR);
+    #endif
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(extint_regs_fun_obj, extint_regs);