HID: lg-g15: Remove unused size argument from lg_*_event() functions

The report-size is already checked in lg_g15_raw_event() before calling
the lg_*_event() functions and these functions don't use the passed
in size at all, drop the unused parameter.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>