py/inlinethumb: Support for core floating point instructions.

Adds support for the following Thumb2 VFP instructions, via the option
MICROPY_EMIT_INLINE_THUMB_FLOAT:

vcmp
vsqrt
vneg
vcvt_f32_to_s32
vcvt_s32_to_f32
vmrs
vmov
vldr
vstr
vadd
vsub
vmul
vdiv
diff --git a/py/mpconfig.h b/py/mpconfig.h
index c78221f..a403a66 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -186,6 +186,11 @@
 #define MICROPY_EMIT_INLINE_THUMB (0)
 #endif
 
+// Whether to enable float support in the Thumb2 inline assembler
+#ifndef MICROPY_EMIT_INLINE_THUMB_FLOAT
+#define MICROPY_EMIT_INLINE_THUMB_FLOAT (1)
+#endif
+
 // Whether to emit ARM native code
 #ifndef MICROPY_EMIT_ARM
 #define MICROPY_EMIT_ARM (0)