sparc: refactor sparc64 isinf{f} selector to C

sparc: refactor sparc64 isinf{f} selector to C

This patch refactors the sparc64 ifunc selector to a C implementation.
Also, the generic symbol is moved to its own implementation file
s_isinf{f}-generic.S).

Checked on sparc64-linux-gnu and sparcv9-linux-gnu.

	* sysdeps/sparc/sparc64/fpu/multiarch/Makefile (sysdeps_calls):
	Add isinff-generic and s_isinf-generic objects.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_isinf-generic.S: New file.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_isinf.c: Likewise.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_isinff-generic.S: Likewise.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_isinff.c: Likewise.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_isinf.S: Remove file.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_isinff.S: Likewise.

Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>