RDMA/cxgb4: Use structs to describe the uABI instead of opencoding

Open coding a loose value is not acceptable for describing the uABI in
RDMA. Provide the missing struct.
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/cxgb4/provider.c

@@ -281,7 +281,9 @@ static struct ib_pd *c4iw_allocate_pd(struct ib_device *ibdev,
 	php->pdid = pdid;
 	php->rhp = rhp;
 	if (context) {
-		if (ib_copy_to_udata(udata, &php->pdid, sizeof(u32))) {
+		struct c4iw_alloc_pd_resp uresp = {.pdid = php->pdid};
+
+		if (ib_copy_to_udata(udata, &uresp, sizeof(uresp))) {
 			c4iw_deallocate_pd(&php->ibpd);
 			return ERR_PTR(-EFAULT);
 		}

include/uapi/rdma/cxgb4-abi.h

@@ -79,4 +79,9 @@ struct c4iw_alloc_ucontext_resp {
 	__u32 status_page_size;
 	__u32 reserved; /* explicit padding (optional for i386) */
 };
+
+struct c4iw_alloc_pd_resp {
+	__u32 pdid;
+};
+
 #endif /* CXGB4_ABI_USER_H */