Input: psmouse - add small delay for IBM trackpoint pass-through mode

There are trackpoint devices that fail to respond to the PS2 command
PSMOUSE_CMD_GETID if immediately queried after the parent device is
deactivated. Add a small delay for the hardware to get in a sane state
before sending any PS2 commands.

One example of such a system is:
Lenovo ThinkPad X120e, model 30515QG
synaptics: Touchpad model: 1, fw: 8.0, id: 0x1e2b1, caps: 0xd001a3/0x940300/0x121c00, board id: 1811, fw id: 797391
Signed-off-by: Stefan Assmann <sassmann@kpanic.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/psmouse-base.c

@@ -1540,6 +1540,10 @@ static int psmouse_connect(struct serio *serio, struct serio_driver *drv)
 	if (error)
 		goto err_clear_drvdata;
 
+	/* give PT device some time to settle down before probing */
+	if (serio->id.type == SERIO_PS_PSTHRU)
+		usleep_range(10000, 15000);
+
 	if (psmouse_probe(psmouse) < 0) {
 		error = -ENODEV;
 		goto err_close_serio;