lib/libm/math: Remove implementations of float conversion functions.

These implementations are incorrect (eg f2d and d2f don't handle special
values like 0.0) and proper versions can be provided by libgcc (or
equivalent depending on the toolchain).

libgcc is now linked with the stmhal port so that library will provide
these functions from now on.

lib/libm/math.c

@@ -36,56 +36,6 @@ typedef union {
     };
 } float_s_t;
 
-typedef union {
-    double d;
-    struct {
-        uint64_t m : 52;
-        uint64_t e : 11;
-        uint64_t s : 1;
-    };
-} double_s_t;
-
-#if defined(__thumb__)
-
-double __attribute__((pcs("aapcs"))) __aeabi_i2d(int32_t x) {
-    return (float)x;
-}
-
-// TODO
-long long __attribute__((pcs("aapcs"))) __aeabi_f2lz(float x) {
-    return (long)x;
-}
-
-double __attribute__((pcs("aapcs"))) __aeabi_f2d(float x) {
-    float_s_t fx={0};
-    double_s_t dx={0};
-
-    fx.f = x;
-    dx.s = (fx.s);
-    dx.e = (fx.e-127+1023) & 0x7FF;
-    dx.m = fx.m;
-    dx.m <<=(52-23); // left justify
-    return dx.d;
-}
-
-float __attribute__((pcs("aapcs"))) __aeabi_d2f(double x) {
-    float_s_t fx={0};
-    double_s_t dx={0};
-
-    dx.d = x;
-    fx.s = (dx.s);
-    fx.e = (dx.e-1023+127) & 0xFF;
-    fx.m = (dx.m>>(52-23)); // right justify
-    return fx.f;
-}
-
-double __aeabi_dmul(double x , double y) {
-    return 0.0;
-
-}
-
-#endif // defined(__thumb__)
-
 #ifndef NDEBUG
 float copysignf(float x, float y) {
     float_s_t fx={.f = x};