fs/fscache/stats.c: fix memory leak

There is a kernel memory leak observed when the proc file
/proc/fs/fscache/stats is read.

The reason is that in fscache_stats_open, single_open is called and the
respective release function is not called during release. Hence fix
with correct release function - single_release().

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=57101

Signed-off-by: Anurup m <[e-mail]>
Cc: shyju pv <[e-mail]>
Cc: Sanil kumar <[e-mail]>
Cc: Nataraj m <[e-mail]>
Cc: Li Zefan <[e-mail]>
Cc: David Howells <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/fscache/stats.c

···
 	.open		= fscache_stats_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
-	.release	= seq_release,
+	.release        = single_release,
 };