backing-dev: kill unused pdflush_proc_obsolete()

After commit b35bd0d9, pdflush_proc_obsolete() is no longer
used. Kill the function and declaration.
Reported-by: Rakesh Pandit <rakesh@tuxera.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/backing-dev.h

@@ -172,8 +172,6 @@ static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
 
 long congestion_wait(int sync, long timeout);
 long wait_iff_congested(struct pglist_data *pgdat, int sync, long timeout);
-int pdflush_proc_obsolete(struct ctl_table *table, int write,
-		void __user *buffer, size_t *lenp, loff_t *ppos);
 
 static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)
 {

mm/backing-dev.c

@@ -1072,23 +1072,3 @@ long wait_iff_congested(struct pglist_data *pgdat, int sync, long timeout)
 	return ret;
 }
 EXPORT_SYMBOL(wait_iff_congested);
-
-int pdflush_proc_obsolete(struct ctl_table *table, int write,
-			void __user *buffer, size_t *lenp, loff_t *ppos)
-{
-	char kbuf[] = "0\n";
-
-	if (*ppos || *lenp < sizeof(kbuf)) {
-		*lenp = 0;
-		return 0;
-	}
-
-	if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
-		return -EFAULT;
-	pr_warn_once("%s exported in /proc is scheduled for removal\n",
-		     table->procname);
-
-	*lenp = 2;
-	*ppos += *lenp;
-	return 2;
-}