[media] em28xx: prepare for supporting multiple LEDs

Introduce a LED role and store all LEDs in an array.
Also provide a helper function to retrieve a specific LED.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
2 files changed