HID: apple: Add support for magic keyboard backlight on T2 Macs

HID: apple: Add support for magic keyboard backlight on T2 Macs

Unlike T2 Macs with Butterfly keyboard, who have their keyboard backlight
on the USB device the T2 Macs with Magic keyboard have their backlight on
the Touchbar backlight device (05ac:8102).

Support for Butterfly keyboards has already been added in
commit 9018eacbe623 ("HID: apple: Add support for keyboard backlight on
certain T2 Macs.") This patch adds support for the Magic keyboards.

Signed-off-by: Orlando Chamberlain <orlandoch.dev@gmail.com>
Co-developed-by: Aditya Garg <gargaditya08@live.com>
Signed-off-by: Aditya Garg <gargaditya08@live.com>
Link: https://patch.msgid.link/E1D444EA-7FD0-42DA-B198-50B0F03298FB@live.com
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>