HID: hid-lg4ff: Add support for G27 LEDs

This patch adds supports for controlling the LED 'tachometer' on
the G27 wheel, via the LED subsystem.

The 5 LEDs are arranged from right (1=grn, 2=grn, 3=yel, 4=yel, 5=red)
and 'mirrored' to the left (10 LEDs in total).

Signed-off-by: Simon Wood <simon@mungewell.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>