crypto: x86/sha256-avx2 - add missing vzeroupper

Since sha256_transform_rorx() uses ymm registers, execute vzeroupper
before returning from it.  This is necessary to avoid reducing the
performance of SSE code.

Fixes: d34a4600 ("crypto: sha256 - Optimized sha256 x86_64 routine using AVX2's RORX instructions")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/x86/crypto/sha256-avx2-asm.S

@@ -716,6 +716,7 @@ SYM_TYPED_FUNC_START(sha256_transform_rorx)
 	popq	%r13
 	popq	%r12
 	popq	%rbx
+	vzeroupper
 	RET
 SYM_FUNC_END(sha256_transform_rorx)