Input: touchkit_ps2 - do not advertise unsupported buttons

Touchkit PS/2 touchscreen does not have left/right/middle buttons and
should not be advertising as capable of generating these events.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/mouse/touchkit_ps2.c

@@ -86,7 +86,8 @@ int touchkit_ps2_detect(struct psmouse *psmouse, bool set_properties)
 
 	if (set_properties) {
 		dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
-		__set_bit(BTN_TOUCH, dev->keybit);
+		dev->keybit[BIT_WORD(BTN_MOUSE)] = 0;
+		dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
 		input_set_abs_params(dev, ABS_X, 0, TOUCHKIT_MAX_XC, 0, 0);
 		input_set_abs_params(dev, ABS_Y, 0, TOUCHKIT_MAX_YC, 0, 0);