hid: egalax: Correct for device resolution report error

The firmware of both supported devices report a X/Y maximum of 4095,
whereas in reality, it is eight times larger. Fixed with this patch.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Stephane Chatty <chatty@enac.fr>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>