[Intel-gfx] [PATCH 32/49] drm/i915/bxt: Implement enable/disable for Display C9 state

[sagar.a.kamble at intel.com]

These are review comments for 
	1) http://lists.freedesktop.org/archives/intel-gfx/2015-March/062167.html
	2) http://lists.freedesktop.org/archives/intel-gfx/2015-March/062168.html

Couple of comments:
1) Defines for DC_STATE_EN* are coming up as part of http://lists.freedesktop.org/archives/intel-gfx/2015-April/063640.html.
Need to rebase this patch on top of it then or vice-versa.
2) DC5 has to enabled back after disabling DC9 if PW2 is power gated.