ci: remove redundant configs disabling kmods

ci: remove redundant configs disabling kmods

The kernel modules are not built by default since below commit.
The Travis CI matrix can be simplified
by removing the redundant option enable_kmods=false,
and by removing some jobs which are redundant.

Note: there is no benefit in checking kmods in Travis Ubuntu.
Anyway different kernel versions and distributions are needed,
and the Technical Board is looking at moving the Linux kmods
out of this repository.

Fixes: 91a861e54164 ("config: disable Linux kernel modules by default")

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Aaron Conole <aconole@redhat.com>
Acked-by: David Marchand <david.marchand@redhat.com>