py/compile: For dynamic compiler, widen literal 1 to get correct shift.

Without this patch, on 64-bit architectures the "1 << (small_int_bits - 1)"
is computed using only 32-bit values (since small_int_bits is a uint8_t)
and so will overflow (and give the wrong result) if small_int_bits is
larger than 32.

py/compile.c

@@ -2685,7 +2685,7 @@ STATIC void compile_node(compiler_t *comp, mp_parse_node_t pn) {
     } else if (MP_PARSE_NODE_IS_SMALL_INT(pn)) {
         mp_int_t arg = MP_PARSE_NODE_LEAF_SMALL_INT(pn);
         #if MICROPY_DYNAMIC_COMPILER
-        mp_uint_t sign_mask = -(1 << (mp_dynamic_compiler.small_int_bits - 1));
+        mp_uint_t sign_mask = -((mp_uint_t)1 << (mp_dynamic_compiler.small_int_bits - 1));
         if ((arg & sign_mask) == 0 || (arg & sign_mask) == sign_mask) {
             // integer fits in target runtime's small-int
             EMIT_ARG(load_const_small_int, arg);