RDMA/netlink: Simplify netlink listener existence check

All users of rdma_nl_chk_listeners() are interested to get boolean answer
if netlink socket has listeners, so update all places to boolean function.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
diff --git a/include/rdma/rdma_netlink.h b/include/rdma/rdma_netlink.h
index c369703..70218e6 100644
--- a/include/rdma/rdma_netlink.h
+++ b/include/rdma/rdma_netlink.h
@@ -96,7 +96,7 @@ int rdma_nl_multicast(struct sk_buff *skb, unsigned int group, gfp_t flags);
 /**
  * Check if there are any listeners to the netlink group
  * @group: the netlink group ID
- * Returns 0 on success or a negative for no listeners.
+ * Returns true on success or false if no listeners.
  */
-int rdma_nl_chk_listeners(unsigned int group);
+bool rdma_nl_chk_listeners(unsigned int group);
 #endif /* _RDMA_NETLINK_H */