[PATCH v2 1/5] math: Simplify and optimize modff implementation

[Wilco Dijkstra]

Hi Adhemerval,
 
> Refactor the generic implementation to use math_config.h definitions,
> and add an alternative one if the ABI supports truncf instructions
> (gated through math-use-builtins-trunc.h).

LGTM.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

Cheers,
Wilco