Optimization: replaced a mov by a movzx
Optimization: replaced a mov by a movzx

MOVZX r32, r/m8: Move byte to doubleword, zero-extension

As we read the shadow memory one byte at a time this is more optimal.

BUG=

Review URL: https://codereview.appspot.com/7698043

git-svn-id: db59699583a60be9a535cd09cdc9132301867226@1379 15e8cca8-e42c-11de-a347-f34a4f72eb7d

ericmckean/syzygy,google/syzygy,ericmckean/syzygy,ericmckean/syzygy,wangming28/syzygy,pombreda/syzygy,wangming28/syzygy,sebmarchand/syzygy,sebmarchand/syzygy,supriyantomaftuh/syzygy,pombreda/syzygy,Eloston/syzygy,Eloston/syzygy,google/syzygy,sebmarchand/syzygy,ericmckean/syzygy,google/syzygy,sebmarchand/syzygy,supriyantomaftuh/syzygy,pombreda/syzygy,ericmckean/syzygy,wangming28/syzygy,pombreda/syzygy,supriyantomaftuh/syzygy,google/syzygy,sebmarchand/syzygy,wangming28/syzygy,supriyantomaftuh/syzygy,pombreda/syzygy