migration/rdma: Clean up qemu_rdma_poll()'s return type

qemu_rdma_poll()'s return type is uint64_t, even though it returns 0,
-1, or @ret, which is int.  Its callers assign the return value to int
variables, then check whether it's negative.  Unclean.

Return int instead.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20230928132019.2544702-2-armbru@redhat.com>

migration/rdma.c

@@ -1469,8 +1469,8 @@ static uint64_t qemu_rdma_make_wrid(uint64_t wr_id, uint64_t index,
  * (of any kind) has completed.
  * Return the work request ID that completed.
  */
-static uint64_t qemu_rdma_poll(RDMAContext *rdma, struct ibv_cq *cq,
-                               uint64_t *wr_id_out, uint32_t *byte_len)
+static int qemu_rdma_poll(RDMAContext *rdma, struct ibv_cq *cq,
+                          uint64_t *wr_id_out, uint32_t *byte_len)
 {
     int ret;
     struct ibv_wc wc;