HID: cougar: Constify cougar_id_table

cougar_id_table[] is not changed and can be made const to allow the
compiler to put it in read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>