powerpc64le: Also avoid IFUNC for __mempcpy

Code used during early static startup in elf/dl-tls.c uses
__mempcpy.

Fixes commit cbd9fd2369 ("Consolidate
TLS block allocation for static binaries with ld.so").

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

sysdeps/powerpc/powerpc64/le/multiarch/dl-symbol-redir-ifunc.h

@@ -20,5 +20,6 @@
 #define _DL_IFUNC_GENERIC_H
 
 asm ("memset = __memset_power8");
+asm ("__mempcpy = __mempcpy_power7");
 
 #endif