Input: fix a double word "is is" in include/linux/input.h

This patch fix a double word "is is" found in in
Documentation/DocBook/device-drivers.xml.
It is because the file was created from comments in sources,
so I have to fix the double words in include/linux/input.h
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

include/linux/input.h

@@ -95,7 +95,7 @@ struct input_value {
  * @grab: input handle that currently has the device grabbed (via
  *	EVIOCGRAB ioctl). When a handle grabs a device it becomes sole
  *	recipient for all input events coming from the device
- * @event_lock: this spinlock is is taken when input core receives
+ * @event_lock: this spinlock is taken when input core receives
  *	and processes a new event for the device (in input_event()).
  *	Code that accesses and/or modifies parameters of a device
  *	(such as keymap or absmin, absmax, absfuzz, etc.) after device