sparc32/sparcv9: add a VIS3 version of fdim

sparc32 passes floating point values in the integer registers. VIS3
instructions gives access to the movwtos instruction to directly
transfer a value from an integer register to a floating point register.
Therefore it makes sense to provide a VIS3 version consisting in the
generic version compiled with -mvis3.

Changelog:
	* math/s_fdim.c: Avoid alias renamed.
	* math/s_fdimf.c: Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/Makefile
	[$(subdir) = math && $(have-as-vis3) = yes] (libm-sysdep_routines):
	Add s_fdimf-vis3, s_fdim-vis3.
	(CFLAGS-s_fdimf-vis3.c): New. Set to -Wa,-Av9d -mvis3.
	(CFLAGS-s_fdim-vis3.c): Likewise.
	sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/s_fdim-vis3.c: New file.
	sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/s_fdim.c: Likewise.