HID: i2c-hid: implement request() callback

This allows HID drivers to also get/set reports through hid_hw_request().

Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>