Input: synaptics - report clickpad property

With the new input property interface, it is possible to report the
special quirks of a device using ioctl/sysfs. This patch sets up the
device as a pointer, and reports the clickpad functionality via the
INPUT_PROP_BUTTONPAD property.

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