RDMA/rxe: Fix the error caused by qp->sk

When sock_create_kern in the function rxe_qp_init_req fails,
qp->sk is set to NULL.

Then the function rxe_create_qp will call rxe_qp_do_cleanup
to handle allocated resource.

Before handling qp->sk, this variable should be checked.

Fixes: 8700e3e7 ("Soft RoCE driver")
Link: https://lore.kernel.org/r/20220822011615.805603-3-yanjun.zhu@linux.devSigned-off-by: Zhu Yanjun <yanjun.zhu@linux.dev>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/sw/rxe/rxe_qp.c

@@ -835,8 +835,10 @@ static void rxe_qp_do_cleanup(struct work_struct *work)
 
 	free_rd_atomic_resources(qp);
 
-	kernel_sock_shutdown(qp->sk, SHUT_RDWR);
-	sock_release(qp->sk);
+	if (qp->sk) {
+		kernel_sock_shutdown(qp->sk, SHUT_RDWR);
+		sock_release(qp->sk);
+	}
 }
 
 /* called when the last reference to the qp is dropped */