pinctrl: aspeed: Add missing header(s)

Do not imply that some of the generic headers may be always included.
Instead, include explicitly what we are direct user of.

Signed-off-by: Andy Shevchenko <[e-mail]>
Acked-by: Linus Walleij <[e-mail]>

drivers/pinctrl/aspeed/pinctrl-aspeed.c

···
 
 #include <linux/mfd/syscon.h>
 #include <linux/platform_device.h>
+#include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include "../core.h"