Input: synaptics - set minimum coordinates as reported by firmware

Newer Synaptics firmware allows to query minimum coordinates reported by
the device, let's use this data.

Acked-by: Chase Douglas <chase.douglas@canonical.com>
Acked-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>