doc: solaris x86 kernel module path

Add instructions for solaris x86 kernel module installation.

Reviewed-on: http://gerrit.openafs.org/8143
Reviewed-by: Ken Dreyer <ktdreyer@ktdreyer.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 5ef5cf48f3d2ba52cf5ed428728215b5b5f8d0b2)

Change-Id: I7bec3361b5f9e47c8b3cfbfbe27e012288ec9780
Reviewed-on: http://gerrit.openafs.org/9565
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>