libatomic: Handle AVX+CX16 AMD like Intel for 16b atomics [PR104688]

We got a response from AMD in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104688#c10
so the following patch starts treating AMD with AVX and CMPXCHG16B
ISAs like Intel by using vmovdqa for atomic load/store in libatomic.
We still don't have confirmation from Zhaoxin and VIA (anything else
with CPUs featuring AVX and CX16?).

2022-11-15  Jakub Jelinek  <jakub@redhat.com>

	PR target/104688
	* config/x86/init.c (__libat_feat1_init): Don't clear
	bit_AVX on AMD CPUs.