octeontx2-af: mcs: 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>
Reviewed-by: Geetha sowjanya <gakula@marvell.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250324080854.408188-1-nichen@iscas.ac.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/marvell/octeontx2/af/mcs_rvu_if.c

@@ -925,7 +925,6 @@ void rvu_mcs_exit(struct rvu *rvu)
 	if (!rvu->mcs_intr_wq)
 		return;
 
-	flush_workqueue(rvu->mcs_intr_wq);
 	destroy_workqueue(rvu->mcs_intr_wq);
 	rvu->mcs_intr_wq = NULL;
 }