hid: egalax: Convert to MT slots

The firmware in the joojoo reports touches sequentially, one per
report, which confuses the current driver. A further complication is
the absense of any indication of a touch frame. This patch converts
the driver to the MT slots protocol, and outputs one full touch frame
per report. This way, proper handling for both firmwares is ensured.

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