RDMA/rdmavt: Delete unnecessary NULL check

There is no need to check 'rdi->qp_dev' for NULL. The field 'qp_dev'
is created in rvt_register_device() which will fail if the 'qp_dev'
allocation fails in rvt_driver_qp_init(). Overwise this pointer
doesn't changed and passed to rvt_qp_exit() by the next step.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 0acb0cc7ec ("IB/rdmavt: Initialize and teardown of qpn table")
Signed-off-by: Natalia Petrova <n.petrova@fintech.ru>
Link: https://lore.kernel.org/r/20230303124408.16685-1-n.petrova@fintech.ru
Signed-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/sw/rdmavt/qp.c

@@ -464,8 +464,6 @@ void rvt_qp_exit(struct rvt_dev_info *rdi)
 	if (qps_inuse)
 		rvt_pr_err(rdi, "QP memory leak! %u still in use\n",
 			   qps_inuse);
-	if (!rdi->qp_dev)
-		return;
 
 	kfree(rdi->qp_dev->qp_table);
 	free_qpn_table(&rdi->qp_dev->qpn_table);