HID: macally: Constify macally_id_table

macally_id_table is not modified 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>