HID: fix merge from wacom into the HID tree

While merging wacom from the input to the hid tree, some
comments have been duplicated. We can also integrate the
test for Synaptics devices in the switch case below, so
it is clear that there will be only one place for such
quirks.

No functional changes are expected in this commit.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>