Use libm_alias_* in soft-fp.
This patch makes the soft-fp implementations of fma functions use the
libm_alias_* macros.
Tested with build-many-glibcs.py that installed stripped shared
libraries are unchanged by the patch.
* soft-fp/fmadf4.c: Include <libm-alias-double.h>.
[!__fma] (fma): Define using libm_alias_double.
* soft-fp/fmasf4.c: Include <libm-alias-float.h>.
[!__fmaf] (fmaf): Define using libm_alias_float.
* soft-fp/fmatf4.c: Include <libm-alias-ldouble.h>.
(fmal): Define using libm_alias_ldouble.