drm/i915: Pass crtc_state and connector state to backlight enable/disable functions

The backlight functions need to determine the pipe and the transcoder the
backlight will be enabled on, so pass crtc_state instead of trying to
dereference the state without holding locks.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100022


Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170612102115.23665-2-maarten.lankhorst@linux.intel.com


Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>