drm/i915/bxt: Enable runtime PM

With the preceding fixes runtime PM should be functional, I could
runtime suspend/resume the device without problems.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: David Weinehall <david.weinehall@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459515767-29228-17-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -2684,7 +2684,7 @@ struct drm_i915_cmd_table {
 #define HAS_RUNTIME_PM(dev)	(IS_GEN6(dev) || IS_HASWELL(dev) || \
 				 IS_BROADWELL(dev) || IS_VALLEYVIEW(dev) || \
 				 IS_CHERRYVIEW(dev) || IS_SKYLAKE(dev) || \
-				 IS_KABYLAKE(dev))
+				 IS_KABYLAKE(dev) || IS_BROXTON(dev))
 #define HAS_RC6(dev)		(INTEL_INFO(dev)->gen >= 6)
 #define HAS_RC6p(dev)		(INTEL_INFO(dev)->gen == 6 || IS_IVYBRIDGE(dev))