HID: add support for MacBookAir4,2 keyboard.

HID: add support for MacBookAir4,2 keyboard.

commit 5d922baa631058c7e37ae33e81c4d3e6437f8d1d upstream.

Added USB device IDs for MacBookAir4,2 keyboard. Device constants were
copied from the MacBookAir3,2 constants. The 4,2 device specification is
reportedly unchanged from the 3,2 predecessor and seems to work well.

Signed-off-by: Joshua V Dillon <jvdillon@gmail.com>
Signed-off-by: Chase Douglas <chase.douglas@canonical.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>