Subzero: Legalize the movzx argument.

The movzx operand must be a register or memory operand.  An immediate operand is not allowed.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4384
R=jpp@chromium.org

Review URL: https://codereview.chromium.org/2598153002 .
1 file changed