The opcodes for 'cmpw r/m16, r16' and 'cmpw r16, r/m16' were swapped, causing a few issues when less than/greater than comparison were performed.

Adds a regression test.

BUG=621926

Committed: https://crrev.com/efa7095e3e360fbadbe909d831ac11b268ca26b0
Review-Url: https://codereview.chromium.org/2103713003
Cr-Original-Commit-Position: refs/heads/master@{#37339}
Cr-Commit-Position: refs/heads/master@{#37345}