Remove now unnecessary kldstat check before attempting to load modules.

Since r233109, kldload has the -n option, which silently ignores options
that are already loaded.

https://lists.freebsd.org/pipermail/freebsd-rc/2018-December/003899.html

Note that this script no longer reports if the module is already loaded,
but it could be argued this wasn't particularly useful information.

PR: docs/234248
Reviewed by: bcr (docs), kib, rgrimes (visual)
Approved by: jilles
Differential Revision: https://reviews.freebsd.org/D18670