staging: zcache: fix pers_pageframes|_max aren't exported in debugfs

Before commit 9c0ad59e ("zcache/debug: Use an array to initialize/use
debugfs attributes"), pers_pageframes|_max are exported in debugfs, but
this commit forgot use array export pers_pageframes|_max. This patch add
pers_pageframes|_max back.
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/zcache/debug.c

@@ -21,6 +21,7 @@ static struct debug_entry {
 	ATTR(pers_ate_eph), ATTR(pers_ate_eph_failed),
 	ATTR(evicted_eph_zpages), ATTR(evicted_eph_pageframes),
 	ATTR(eph_pageframes), ATTR(eph_pageframes_max),
+	ATTR(pers_pageframes), ATTR(pers_pageframes_max),
 	ATTR(eph_zpages), ATTR(eph_zpages_max),
 	ATTR(pers_zpages), ATTR(pers_zpages_max),
 	ATTR(last_active_file_pageframes),