Don't put SSE2/AVX/AVX512 memmove/memset in ld.so

Since memmove and memset in ld.so don't use IFUNC, don't put SSE2, AVX
and AVX512 memmove and memset in ld.so.

	* sysdeps/x86_64/multiarch/memmove-avx-unaligned-erms.S: Skip
	if not in libc.
	* sysdeps/x86_64/multiarch/memmove-avx512-unaligned-erms.S:
	Likewise.
	* sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S:
	Likewise.
	* sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S:
	Likewise.