Use libm_alias_double for s390.

Use libm_alias_double for s390.

Continuing the preparation for additional _FloatN / _FloatNx function
aliases, this patch makes s390 libm function implementations use
libm_alias_double to define function aliases.  This allows
sysdeps/unix/sysv/linux/s390/fpu/s_fma.c to be removed, as
libm_alias_double handles symbol versioning for long double compat
symbols.

Tested with build-many-glibcs.py for s390-linux-gnu and
s390x-linux-gnu that installed stripped shared libraries are unchanged
by the patch.

	* sysdeps/s390/fpu/s_fma.c: Include <libm-alias-double.h>.
	[!__fma] (fma): Define using libm_alias_double.
	* sysdeps/unix/sysv/linux/s390/fpu/s_fma.c: Remove.