drm/i915: wrap GEN6_PMIMR changes

Just like we're doing with the other IMR changes.

One of the functional changes is that not every caller was doing the
POSTING_READ.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index a846206..8222f24 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -781,5 +781,8 @@
 extern void ilk_enable_gt_irq(struct drm_i915_private *dev_priv, uint32_t mask);
 extern void ilk_disable_gt_irq(struct drm_i915_private *dev_priv,
 			       uint32_t mask);
+extern void snb_enable_pm_irq(struct drm_i915_private *dev_priv, uint32_t mask);
+extern void snb_disable_pm_irq(struct drm_i915_private *dev_priv,
+			       uint32_t mask);
 
 #endif /* __INTEL_DRV_H__ */