When compiling with all warnings enabled, some defines can lead to
warning due to missing unsigned type suffix:
warning: integer overflow in expression [-Woverflow]
This fix should not affected behavior at all, since calculation with
such overflows lead to the same actual address when writing to that
location. However, it makes the warning disappear and also defines
the right data type for a memory location.
We currently default to "-mfloat-abi=hard -mfpu=fpv4-sp-d16" for M4F cores, and
and variations of "-mfloat-abi=soft" for the others. Keep the M4F default, and
move others to no FP flags for consistency, but allow overriding these flags
via the FP_FLAGS environment variable.
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>