move check for AD*X to rsaz-avx2.pl.

This ensures high performance is situations when assembler supports
AVX2, but not AD*X.

(Imported from upstream's 82a9dafe32e1e39b5adff18f9061e43d8df3d3c5)

Change-Id: Ie67f49a1c5467807139b6a8a0d4e62162d8a974f
2 files changed