tcm_fc: Avoid debug overhead when not debugging

Stop doing a pile of work related to debugging messages when
the ft_debug_logging flag is not set. Use unlikely to add the
check in a way that the check can be inlined without inlining the
whole thing.

Signed-off-by: Mark Rustad <[e-mail]>
Signed-off-by: Nicholas Bellinger <[e-mail]>

drivers/target/tcm_fc/tcm_fc.h

···
 extern struct mutex ft_lport_lock;
 extern struct fc4_prov ft_prov;
 extern struct target_fabric_configfs *ft_configfs;
+extern unsigned int ft_debug_logging;
 
 /*
  * Fabric methods.

drivers/target/tcm_fc/tfc_cmd.c

···
 /*
  * Dump cmd state for debugging.
  */
-void ft_dump_cmd(struct ft_cmd *cmd, const char *caller)
+static void _ft_dump_cmd(struct ft_cmd *cmd, const char *caller)
 {
 	struct fc_exch *ep;
 	struct fc_seq *sp;
···
 			caller, cmd, ep->sid, ep->did, ep->oxid, ep->rxid,
 			sp->id, ep->esb_stat);
 	}
+}
+
+void ft_dump_cmd(struct ft_cmd *cmd, const char *caller)
+{
+	if (unlikely(ft_debug_logging))
+		_ft_dump_cmd(cmd, caller);
 }
 
 static void ft_free_cmd(struct ft_cmd *cmd)