Fix alignment-violating cast.

Change-Id: Id8b69bb6103dd938f4c6d0d2ec24f3d50ba5513c
Update-Note: fixes b/70034392
Reviewed-on: https://boringssl-review.googlesource.com/23744
Commit-Queue: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/crypto/fipsmodule/bn/rsaz_exp.c b/crypto/fipsmodule/bn/rsaz_exp.c
index d0090a6..cb9a233 100644
--- a/crypto/fipsmodule/bn/rsaz_exp.c
+++ b/crypto/fipsmodule/bn/rsaz_exp.c
@@ -227,7 +227,9 @@
 
 		rsaz_1024_sqr_avx2(result, result, m, k0, 5);
 
-		wvalue = *((const unsigned short*)&p_str[index / 8]);
+		uint16_t wvalue_16;
+		memcpy(&wvalue_16, &p_str[index / 8], sizeof(wvalue_16));
+		wvalue = wvalue_16;
 		wvalue = (wvalue>> (index%8)) & 31;
 		index-=5;