HID: wacom: generic: Correct pad syncing

Only sync the pad once per report, not once per collection.
Also avoid syncing the pad on battery reports.

Fixes: f8b6a747

 ("HID: wacom: generic: Support multiple tools per report")
Cc: <stable@vger.kernel.org> # v4.17+
Signed-off-by: Aaron Armstrong Skomra <aaron.skomra@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>