RDMA: Check create_flags during create_qp

Each driver should check that the QP attrs create_flags is supported.
Unfortuantely when create_flags was added to the QP attrs the drivers were
not updated. uverbs_ex_cmd_mask was used to block it - even though kernel
drivers use these flags too.

Check that flags is zero in all drivers that don't use it, remove
IB_USER_VERBS_EX_CMD_CREATE_QP from uverbs_ex_cmd_mask. Fix the error code
to be EOPNOTSUPP.

Link: https://lore.kernel.org/r/8-v1-caa70ba3d1ab+1436e-ucmd_mask_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
index 7d32cb2..21d2ab3 100644
--- a/drivers/infiniband/sw/rxe/rxe_verbs.c
+++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
@@ -395,6 +395,9 @@ static struct ib_qp *rxe_create_qp(struct ib_pd *ibpd,
 		uresp = udata->outbuf;
 	}
 
+	if (init->create_flags)
+		return ERR_PTR(-EOPNOTSUPP);
+
 	err = rxe_qp_chk_init(rxe, init);
 	if (err)
 		goto err1;