HID: alps: Declare U1_UNICORN_LEGACY support

U1_UNICORN_LEGACY id was added to the driver, but was not declared
in the device id table, making it impossible to use.

Fixes: 640e403b

 ("HID: alps: Add AUI1657 device ID")
Signed-off-by: Artem Borisov <dedsa2002@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>