drm/i915: bdw: fix RC6 enabled status reporting and disable runtime PM

On BDW we don't enable RC6 at the moment, but this isn't reflected in
the (sanitized) i915.enable_rc6 option. So make enable_rc6 report
correctly that RC6 is disabled, which will also effectively disable RPM
on BDW (since RPM depends on RC6).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77565

Signed-off-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -3260,6 +3260,10 @@ static int sanitize_rc6_option(const struct drm_device *dev, int enable_rc6)
 	if (INTEL_INFO(dev)->gen == 5 && !IS_IRONLAKE_M(dev))
 		return 0;
 
+	/* Disable RC6 on Broadwell for now */
+	if (IS_BROADWELL(dev))
+		return 0;
+
 	/* Respect the kernel parameter if it is set */
 	if (enable_rc6 >= 0) {
 		int mask;