HID: apple: add fnmode=4 to disable translation of fkeys and make it default on Macs with Touch Bar

The kernel now has a dedicated driver for Touch Bar on Macs. Since
function keys can now be accessed via the Touch Bar, emulating them
using non standard ways like Fn+1=F1 should be avoided.

This patch adds an fnmode=4 which ignores only the Function key
translation, and is enabled by default on MacBook Pros with a Touch
Bar.

Signed-off-by: Aditya Garg <gargaditya08@live.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>