x86: Remove unused file wmemcmp-sse4

The memcmp-sse4 was removed in:

commit 7cbc03d0
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date:   Fri Apr 15 12:28:00 2022 -0500

    x86: Remove memcmp-sse4.S

so this file does nothing.