Input: psmouse - introduce notion of SMBus companions

Prepare PS/2 mouse drivers to work with devices that are accessible both
via PS/2 and SMBus, which provides higher bandwidth, and thus suits better
for modern multi-touch devices.

We expect that SMBus drivers will take control over the device, so when
we detect SMBus "protocol" we forego registering input device, or enabling
PS/2 device reports (as it usually makes device unresponsive to access over
SMBus).

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