drm/i915 invalidate indirect state pointers at end of ring exec

This is required by the spec, and without this some 3D programs will
hang after resume from RC6 we enable that.

Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

diff --cc drivers/gpu/drm/i915/i915_dma.c
Simple merge

diff --cc drivers/gpu/drm/i915/i915_reg.h
Simple merge

diff --cc drivers/gpu/drm/i915/intel_ringbuffer.c
Simple merge