previously the I411 format used movd to read U, V pixels.
But this reads 4 bytes, and can cause a memory exception.
pinsrw can be used, but fails on drmemory 1.5, and is slow.
So in this change a movzxw is used to read 2 bytes into EBX,
then copy to xmm0 with movd.
Slightly slower, but no memory exception
Was LibYUVConvertTest.I411ToARGB_Opt (577 ms)
Now LibYUVConvertTest.I411ToARGB_Opt (608 ms)

TBR=harryjin@google.com
BUG=libyuv:525

Review URL: https://codereview.chromium.org/1457783004 .