Input: bcm5974 - add support for MacBookPro8

This patch add multitouch support for the MacBookPro8,1 and
MacBookPro8,2 models.

Cc: stable@kernel.org
Signed-off-by: Andy Botting <andy@andybotting.com>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>