Revert "drm/i915: enable rc6 by default"

This reverts commit a51f7a66.

We still have a few Ironlake and Sandybridge machines which fail when
RC6 is enabled. Better luck next release?
Signed-off-by: Keith Packard <keithp@keithp.com>

drivers/gpu/drm/i915/i915_drv.c

@@ -52,7 +52,7 @@ module_param_named(powersave, i915_powersave, int, 0600);
 unsigned int i915_semaphores = 0;
 module_param_named(semaphores, i915_semaphores, int, 0600);
 
-unsigned int i915_enable_rc6 = 1;
+unsigned int i915_enable_rc6 = 0;
 module_param_named(i915_enable_rc6, i915_enable_rc6, int, 0600);
 
 unsigned int i915_enable_fbc = 0;