powerpc: Fix linknamespace introduced by 4d801563

This patch fixes the linknamespace issues add on wcscpy refactor
for powerpc-linux-gnu-power4 as shown by the tests:

FAIL: conform/POSIX/fnmatch.h/linknamespace
FAIL: conform/POSIX/glob.h/linknamespace
FAIL: conform/POSIX/wordexp.h/linknamespace
FAIL: conform/XPG4/fnmatch.h/linknamespace
FAIL: conform/XPG4/glob.h/linknamespace
FAIL: conform/XPG4/wordexp.h/linknamespace
FAIL: conform/XPG42/fnmatch.h/linknamespace
FAIL: conform/XPG42/glob.h/linknamespace
FAIL: conform/XPG42/wordexp.h/linknamespace

[initial] wordexp -> [libc.a(wordexp.o)] fnmatch -> [libc.a(fnmatch.o)] __wcscat -> [libc.a(wcscat.o)] __wcscpy -> [libc.a(wcscpy.o)] wcscpy

Checked on powerpc-linux-gnu-power4.

	* sysdeps/powerpc/powerpc32/power4/multiarch/wcscpy.c: Define ifunc
	symbol as __wcspcy instead of wcscpy.