scsi: libfc: Supply some missing kerneldoc struct/function attributes/params

Fixes the following W=1 kernel build warning(s):

 drivers/scsi/libfc/fc_exch.c:66: warning: Function parameter or member 'left' not described in 'fc_exch_pool'
 drivers/scsi/libfc/fc_exch.c:66: warning: Function parameter or member 'right' not described in 'fc_exch_pool'
 drivers/scsi/libfc/fc_exch.c💯 warning: Function parameter or member 'lport' not described in 'fc_exch_mgr'
 drivers/scsi/libfc/fc_exch.c:727: warning: Function parameter or member 'ep' not described in 'fc_invoke_resp'
 drivers/scsi/libfc/fc_exch.c:727: warning: Function parameter or member 'sp' not described in 'fc_invoke_resp'
 drivers/scsi/libfc/fc_exch.c:727: warning: Function parameter or member 'fp' not described in 'fc_invoke_resp'

Link: https://lore.kernel.org/r/20200713074645.126138-2-lee.jones@linaro.org
Cc: Hannes Reinecke <hare@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/libfc/fc_exch.c

@@ -49,6 +49,8 @@ static struct workqueue_struct *fc_exch_workqueue;
  * @total_exches: Total allocated exchanges
  * @lock:	  Exch pool lock
  * @ex_list:	  List of exchanges
+ * @left:	  Cache of free slot in exch array
+ * @right:	  Cache of free slot in exch array
  *
  * This structure manages per cpu exchanges in array of exchange pointers.
  * This array is allocated followed by struct fc_exch_pool memory for
@@ -60,7 +62,6 @@ struct fc_exch_pool {
 	u16		 next_index;
 	u16		 total_exches;
 
-	/* two cache of free slot in exch array */
 	u16		 left;
 	u16		 right;
 } ____cacheline_aligned_in_smp;
@@ -74,6 +75,7 @@ struct fc_exch_pool {
  * @ep_pool:	    Reserved exchange pointers
  * @pool_max_index: Max exch array index in exch pool
  * @pool:	    Per cpu exch pool
+ * @lport:	    Local exchange port
  * @stats:	    Statistics structure
  *
  * This structure is the center for creating exchanges and sequences.
@@ -702,6 +704,9 @@ int fc_seq_exch_abort(const struct fc_seq *req_sp, unsigned int timer_msec)
 
 /**
  * fc_invoke_resp() - invoke ep->resp()
+ * @ep:	   The exchange to be operated on
+ * @fp:	   The frame pointer to pass through to ->resp()
+ * @sp:	   The sequence pointer to pass through to ->resp()
  *
  * Notes:
  * It is assumed that after initialization finished (this means the