backlight: extend event support to also support poll()
backlight: extend event support to also support poll()

Extend the backlight event support to also allow the use of
poll()/select() on actual_brightness.

We already have the entire event hookup anyway, adding a single
function call in one line to get functionality like that is a really
good deal.

Signed-off-by: Henrique de Moraes Holschuh <1416ae054606eb9be8fa0d7696a4ddff667a3601@hmh.eng.br>
Signed-off-by: Richard Purdie <a03894c799ea916bd571ce8f12ed88f6fb3400f7@linux.intel.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs