Input: axp20x-pek - make device attributes static

The two device attrbitues are not declared outside this file
so make them static to avoid the following warnings:

drivers/input/misc/axp20x-pek.c:194:1: warning: symbol 'dev_attr_startup' was not declared. Should it be static?
drivers/input/misc/axp20x-pek.c:195:1: warning: symbol 'dev_attr_shutdown' was not declared. Should it be static?
Signed-off-by: Ben Dooks (Codethink) <ben.dooks@codethink.co.uk>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20191217152541.2167080-1-ben.dooks@codethink.co.ukSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/axp20x-pek.c

@@ -191,8 +191,9 @@ static ssize_t axp20x_store_attr_shutdown(struct device *dev,
 				 axp20x_pek->info->shutdown_mask, buf, count);
 }
 
-DEVICE_ATTR(startup, 0644, axp20x_show_attr_startup, axp20x_store_attr_startup);
-DEVICE_ATTR(shutdown, 0644, axp20x_show_attr_shutdown,
+static DEVICE_ATTR(startup, 0644, axp20x_show_attr_startup,
+		   axp20x_store_attr_startup);
+static DEVICE_ATTR(shutdown, 0644, axp20x_show_attr_shutdown,
 		   axp20x_store_attr_shutdown);
 
 static struct attribute *axp20x_attrs[] = {