pinctrl: microchip-sgpio: 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 <andriy.shevchenko@linux.intel.com>

drivers/pinctrl/pinctrl-microchip-sgpio.c

@@ -15,13 +15,15 @@
 #include <linux/mfd/ocelot.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
-#include <linux/pinctrl/pinmux.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/regmap.h>
 #include <linux/reset.h>
 #include <linux/spinlock.h>
 
+#include <linux/pinctrl/pinconf.h>
+#include <linux/pinctrl/pinmux.h>
+
 #include "core.h"
 #include "pinconf.h"