Input: psmouse - fix Synaptics detection when protocol is disabled

When Synaptics protocol is disabled, we still need to try and detect the
hardware, so we can switch to SMBus device if SMbus is detected, or we know
that it is Synaptics device and reset it properly for the bare PS/2
protocol.

Fixes: c378b511 ("Input: psmouse - factor out common protocol probing code")
Reported-by: Matteo Croce <mcroce@redhat.com>
Tested-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>