buildroot

rtai: Install modules in /lib/modules/<version>/rtai

The /lib/modules/<version>/kernel/ is completely rewritten by the
kernel module installation, so third party modules should be outside
of this directory.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>