RDMA/rxe: Extend rxe user ABI to support atomic write

Define an atomic_wr array to store 8-byte value.

Link: https://lore.kernel.org/r/1669905432-14-4-git-send-email-yangx.jy@fujitsu.comSigned-off-by: Xiao Yang <yangx.jy@fujitsu.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

include/uapi/rdma/rdma_user_rxe.h

@@ -146,6 +146,7 @@ struct rxe_dma_info {
 	__u32			reserved;
 	union {
 		__DECLARE_FLEX_ARRAY(__u8, inline_data);
+		__DECLARE_FLEX_ARRAY(__u8, atomic_wr);
 		__DECLARE_FLEX_ARRAY(struct rxe_sge, sge);
 	};
 };