IB/rxe: avoid unnecessary NULL check

Before goto err2, the variable qp is checked. So it is not necessary
to check qp in label err2.

Signed-off-by: Zhu Yanjun <yanjun.zhu@oracle.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/sw/rxe/rxe_recv.c

@@ -256,8 +256,7 @@ static int hdr_check(struct rxe_pkt_info *pkt)
 	return 0;
 
 err2:
-	if (qp)
-		rxe_drop_ref(qp);
+	rxe_drop_ref(qp);
 err1:
 	return -EINVAL;
 }