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
1 file changed