RDMA/srpt: Fix typo in srpt_unregister_mad_agent docstring

htmldocs fails with:

drivers/infiniband/ulp/srpt/ib_srpt.c:630: warning: Function parameter or member 'port_cnt' not described in 'srpt_unregister_mad_agent'

Fixes: 372a1786 ("IB/srpt: Fix memory leak in srpt_add_one")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/srpt/ib_srpt.c

@@ -622,7 +622,7 @@ static int srpt_refresh_port(struct srpt_port *sport)
 /**
  * srpt_unregister_mad_agent - unregister MAD callback functions
  * @sdev: SRPT HCA pointer.
- * #port_cnt: number of ports with registered MAD
+ * @port_cnt: number of ports with registered MAD
  *
  * Note: It is safe to call this function more than once for the same device.
  */