power: supply: mt6370: 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/20250312073729.1430053-1-nichen@iscas.ac.cn
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Author: Chen Ni

drivers/power/supply/mt6370-charger.c

@@ -772,7 +772,6 @@ static void mt6370_chg_destroy_wq(void *data)
 {
 	struct workqueue_struct *wq = data;
 
-	flush_workqueue(wq);
 	destroy_workqueue(wq);
 }