powerpc: Use default strcpy optimization for POWER7

This patches uses the default strcpy/stpcpy implementation for
POWER7/PPC64.  This is faster in mostly inputs for benchtests
and for multiarch the implementation uses the POWER7 strlen and
memcpy.

	* string/stpcpy.c (__stpcpy): Use STPCPY to redefine symbol name and
	cleanup macro usage.
	* string/strcpy.c (strcpt): Use STRCPY to redefine symbol name.
	* sysdeps/powerpc/powerpc64/multiarch/stpcpy-power7.S: Remove file.
	* sysdeps/powerpc/powerpc64/multiarch/stpcpy-ppc64.S: Likewise.
	* sysdeps/powerpc/powerpc64/multiarch/strcpy-power7.S: Likewise.
	* sysdeps/powerpc/powerpc64/multiarch/strcpy-ppc64.S: Likewise.
	* sysdeps/powerpc/powerpc64/power7/stpcpy.S: Likewise.
	* sysdeps/powerpc/powerpc64/power7/strcpy.S: Likewise.
	* sysdeps/powerpc/powerpc64/power7/strcpy.c: Likewise.
	* sysdeps/powerpc/powerpc64/stpcpy.S: Likewise.
	* sysdeps/powerpc/powerpc64/strcpy.S: Likewise.
	* sysdeps/powerpc/powerpc64/multiarch/stpcpy.c
	[SHARED && IS_IN (libc)]: Include <string/strcpy.c>.
	* sysdeps/powerpc/powerpc64/multiarch/stpcpy.c
	[SHARED && IS_IN (libc)]: Include <string/stpcpy.c>.
	* sysdeps/powerpc/powerpc64/multiarch/stpcpy-power7.c: New file.
	* sysdeps/powerpc/powerpc64/multiarch/stpcpy-ppc64.c: Likewise.
	* sysdeps/powerpc/powerpc64/multiarch/strcpy-power7.c: Likewise.
	* sysdeps/powerpc/powerpc64/multiarch/strcpy-ppc64.c: Likewise.
	* sysdeps/powerpc/powerpc64/power7/strcpy.c: Likewise.