sha: Add SSSE3 check to SHAEXT SHA-256 implementation.

The implementation does use SSSE3 (palignr, pshufb).

Change-Id: I86a44c1dc505b27b87fdc3cc7f6e8115abb3dcc9
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/64567
Reviewed-by: David Benjamin <davidben@google.com>
Reviewed-by: Bob Beck <bbe@google.com>
Commit-Queue: Bob Beck <bbe@google.com>

crypto/fipsmodule/sha/internal.h

diff --git a/crypto/fipsmodule/sha/internal.h b/crypto/fipsmodule/sha/internal.h
index b55ea8e..0c05d73 100644
--- a/crypto/fipsmodule/sha/internal.h
+++ b/crypto/fipsmodule/sha/internal.h
@@ -126,7 +126,8 @@
 
 #define SHA256_ASM_HW
 OPENSSL_INLINE int sha256_hw_capable(void) {
-  return CRYPTO_is_x86_SHA_capable();
+  // Note that the original assembly did not check SSSE3.
+  return CRYPTO_is_x86_SHA_capable() && CRYPTO_is_SSSE3_capable();
 }
 
 #define SHA256_ASM_AVX