libfc: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

The uses of "rcu_assign_pointer()" are NULLing out the pointers.
According to RCU_INIT_POINTER()'s block comment:
"1.   This use of RCU_INIT_POINTER() is NULLing out the pointer"
it is better to use it instead of rcu_assign_pointer() because it has a
smaller overhead.

The following Coccinelle semantic patch was used:
@@
@@

- rcu_assign_pointer
+ RCU_INIT_POINTER
  (..., NULL)
Signed-off-by: Andreea-Cristina Bernat <bernat.ada@gmail.com>
Acked-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/libfc/fc_libfc.c

@@ -296,9 +296,9 @@ void fc_fc4_deregister_provider(enum fc_fh_type type, struct fc4_prov *prov)
 	BUG_ON(type >= FC_FC4_PROV_SIZE);
 	mutex_lock(&fc_prov_mutex);
 	if (prov->recv)
-		rcu_assign_pointer(fc_passive_prov[type], NULL);
+		RCU_INIT_POINTER(fc_passive_prov[type], NULL);
 	else
-		rcu_assign_pointer(fc_active_prov[type], NULL);
+		RCU_INIT_POINTER(fc_active_prov[type], NULL);
 	mutex_unlock(&fc_prov_mutex);
 	synchronize_rcu();
 }