Input: add input_set_capability() helper

Add input_set_capability() helper used to indicate that an input
device supports a certain event without need to manipulate bitmaps
directly.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/include/linux/input.h b/include/linux/input.h
index 7b6d7c4..1789ee9 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -1160,6 +1160,8 @@
 	input_event(dev, EV_SYN, SYN_REPORT, 0);
 }
 
+void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int code);
+
 static inline void input_set_abs_params(struct input_dev *dev, int axis, int min, int max, int fuzz, int flat)
 {
 	dev->absmin[axis] = min;