Input: ad7879 - consolidate PM methods

The PM methods are basically the same for SPI and I2C busses, so let's
use the same dev_pm_ops for both of them.

Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/touchscreen/ad7879.h b/drivers/input/touchscreen/ad7879.h
index 6b45a27..6fd13c4 100644
--- a/drivers/input/touchscreen/ad7879.h
+++ b/drivers/input/touchscreen/ad7879.h
@@ -21,8 +21,8 @@
 	int (*write)(struct device *dev, u8 reg, u16 val);
 };
 
-void ad7879_suspend(struct ad7879 *);
-void ad7879_resume(struct ad7879 *);
+extern const struct dev_pm_ops ad7879_pm_ops;
+
 struct ad7879 *ad7879_probe(struct device *dev, u8 devid, unsigned irq,
 			    const struct ad7879_bus_ops *bops);
 void ad7879_remove(struct ad7879 *);