Input: synaptics-rmi4 - fix documentation of rmi_2d_sensor_platform_data

Typos...
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

include/linux/rmi.h

@@ -108,7 +108,7 @@ struct rmi_2d_sensor_platform_data {
  * @buttonpad - the touchpad is a buttonpad, so enable only the first actual
  * button that is found.
  * @trackstick_buttons - Set when the function 30 is handling the physical
- * buttons of the trackstick (as a PD/2 passthrough device.
+ * buttons of the trackstick (as a PS/2 passthrough device).
  * @disable - the touchpad incorrectly reports F30 and it should be ignored.
  * This is a special case which is due to misconfigured firmware.
  */