ci: remove redundant drivers enabling

ci: remove redundant drivers enabling

No need to explicitly enable drivers bus/vdev and mempool/ring.

bus/vdev is always enabled since
commit 2e33309ebe03 ("config: enable/disable drivers in Arm builds")

mempool/ring is always enabled since
commit 81c2337e044d ("build: make ring mempool driver mandatory")

The driver net/null is kept to allow running test-null.sh.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: David Marchand <david.marchand@redhat.com>