IB/rxe: Avoid accessing timers for non RC QPs

This patch avoids RNR NAK timer and retransmit timer initialization and
cleanup for non RC QPs (such as UD QP, GSI QP).

Reviewed-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>