rx: Do not include linux/module.h

rx: Do not include linux/module.h

This isn't available in userspace; we don't need it, so just don't
include it at all.

This was introduced in 9cd98379. I had thought it fixed a build
failure, but I believe now I just made a mistake during build.

Change-Id: If97d8e3204b27acd053ec021ddd8cd1527dad3c5
Reviewed-on: http://gerrit.openafs.org/8112
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: Derrick Brashear <shadow@your-file-system.com>