infiniband: fix core/verbs.c kernel-doc notation

Add missing function parameter descriptions:

../drivers/infiniband/core/verbs.c:257: warning: Function parameter or member 'flags' not described in '__ib_alloc_pd'
../drivers/infiniband/core/verbs.c:257: warning: Function parameter or member 'caller' not described in '__ib_alloc_pd'

Link: https://lore.kernel.org/r/20191010035240.011497492@gmail.com
Signed-off-by: Randy Dunlap <rd.dunlab@gmail.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/verbs.c

@@ -244,6 +244,8 @@ EXPORT_SYMBOL(rdma_port_get_link_layer);
 /**
  * ib_alloc_pd - Allocates an unused protection domain.
  * @device: The device on which to allocate the protection domain.
+ * @flags: protection domain flags
+ * @caller: caller's build-time module name
  *
  * A protection domain object provides an association between QPs, shared
  * receive queues, address handles, memory regions, and memory windows.