HID: hidraw: add support uniq ioctl

Add support for reading out the uniq information from the underlying HID
device. This might be the iSerialNumber in case of USB or the BD_ADDR in
case of Bluetooth.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>