delayacct: cleanup flags in struct task_delay_info and functions use it

Flags in struct task_delay_info is used to distinguish the difference
between swapin and blkio delay acountings.  But after patch "delayacct:
support swapin delay accounting for swapping without blkio", there is no
need to do that since swapin and blkio delay accounting use their own
functions.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Yang Yang <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Zeal Robot <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: yangyang20220519

include/linux/delayacct.h

@@ -12,7 +12,6 @@
 #ifdef CONFIG_TASK_DELAY_ACCT
 struct task_delay_info {
 	raw_spinlock_t	lock;
-	unsigned int	flags;	/* Private per-task flags */
 
 	/* For each stat XXX, add following, aligned appropriately
 	 *
@@ -74,18 +73,6 @@ extern void __delayacct_thrashing_end(void);
 extern void __delayacct_swapin_start(void);
 extern void __delayacct_swapin_end(void);
 
-static inline void delayacct_set_flag(struct task_struct *p, int flag)
-{
-	if (p->delays)
-		p->delays->flags |= flag;
-}
-
-static inline void delayacct_clear_flag(struct task_struct *p, int flag)
-{
-	if (p->delays)
-		p->delays->flags &= ~flag;
-}
-
 static inline void delayacct_tsk_init(struct task_struct *tsk)
 {
 	/* reinitialize in case parent's non-null pointer was dup'ed*/
@@ -184,10 +171,6 @@ static inline void delayacct_swapin_end(void)
 }
 
 #else
-static inline void delayacct_set_flag(struct task_struct *p, int flag)
-{}
-static inline void delayacct_clear_flag(struct task_struct *p, int flag)
-{}
 static inline void delayacct_init(void)
 {}
 static inline void delayacct_tsk_init(struct task_struct *tsk)