Input: bcm5974 - only setup button urb for TYPE1 devices

The early generations with this trackpad used the separate mouse
interface to produce button events. With the introduction of the
button pads, this information was moved to the trackpad interface,
leaving the mouse interface unused. The driver is still setting up
both interfaces, which has not caused any problems - until now.

It turns out that without the CONFIG_USB_EHCI_TT_NEWSCHED option, the
driver may return an ENOSPC upon bt_urb submission, resulting in a
failure to open the device. This happens everytime on the MacBookPro
Retina (and likely on other mid-2012 models), but earlier MacBook
models seem to work fine.

This patch skips the bt_urb setup for TYPE2 devices, which arguably
should have been done in the first place.

Tested-by: Benjamin Tissoires <benjamin.tissoires@enac.fr>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>