Merge tag 'topic/backlight_for_lag-2018-01-29' of git://anongit.freedesktop.org/drm...

This contains the backlight portion of Meghana Madhyastha's patch set to
migrate the backlight helpers from tinydrm to the backlight subsystem.

https://patchwork.freedesktop.org/series/36522/

Cc: Meghana Madhyastha <meghana.madhyastha@gmail.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
# gpg: Signature made Mon 29 Jan 2018 02:25:40 PM EST
# gpg:                using RSA key 7F17297CC4A076740CB3E42A96F70DFDA84A070A
# gpg: Good signature from "Sean Paul <seanpaul@chromium.org>" [unknown]
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 1C5E AB9E D7C9 DDE9 E7F2  087C 732C 0025 72DC AF79
#      Subkey fingerprint: 7F17 297C C4A0 7674 0CB3  E42A 96F7 0DFD A84A 070A
Link: https://patchwork.freedesktop.org/patch/msgid/20180129192950.bvmhkz3h42t5a25r@art_vandelay