scsi: fnic: Remove redundant flush_workqueue() calls

destroy_workqueue() already drains the queue before destroying it, so
there is no need to flush it explicitly.

Remove the redundant flush_workqueue() calls.

This was generated with coccinelle:

@@
expression E;
@@
- flush_workqueue(E);
  destroy_workqueue(E);

Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Link: https://lore.kernel.org/r/20250312074320.1430175-1-nichen@iscas.ac.cn
Reviewed-by: Karan Tilak Kumar <kartilak@cisco.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: Chen Ni

drivers/scsi/fnic/fnic_main.c

@@ -1365,10 +1365,9 @@ static void __exit fnic_cleanup_module(void)
 	if (pc_rscn_handling_feature_flag == PC_RSCN_HANDLING_FEATURE_ON)
 		destroy_workqueue(reset_fnic_work_queue);
 
-	if (fnic_fip_queue) {
-		flush_workqueue(fnic_fip_queue);
+	if (fnic_fip_queue)
 		destroy_workqueue(fnic_fip_queue);
-	}
+
 	kmem_cache_destroy(fnic_sgl_cache[FNIC_SGL_CACHE_MAX]);
 	kmem_cache_destroy(fnic_sgl_cache[FNIC_SGL_CACHE_DFLT]);
 	kmem_cache_destroy(fnic_io_req_cache);