yasm: Merge a clang warning fix.

Namely, https://github.com/yasm/yasm/commit/a2cbb10ee1b90b73647667ac849c74d65761d412
TBR=ajwong
Review URL: https://chromiumcodereview.appspot.com/9533001

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/yasm/patched-yasm@124103 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
diff --git a/libyasm/md5.c b/libyasm/md5.c
index 80b550c..0260348 100644
--- a/libyasm/md5.c
+++ b/libyasm/md5.c
@@ -163,7 +163,7 @@
         putu32(ctx->buf[1], digest + 4);
         putu32(ctx->buf[2], digest + 8);
         putu32(ctx->buf[3], digest + 12);
-        memset(ctx, 0, sizeof(ctx));    /* In case it's sensitive */
+        memset(ctx, 0, sizeof(*ctx));    /* In case it's sensitive */
 }
 
 #ifndef ASM_MD5