drm/i915: Extract intel_fifo_underrun.c

Prep work for some nice documentation. Requires that we export the
display irq enable/disable functions on ilk/ibx. But we already export
them for vlv/i915. So not more inconsistency.

v2: Rebase on top of skl stage 1.

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 94993d2..321701d 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -755,12 +755,17 @@
 	return INTEL_INFO(crtc->base.dev)->num_sprites[crtc->pipe] + 1;
 }
 
-/* i915_irq.c */
+/* intel_fifo_underrun.c */
 bool intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
 					   enum pipe pipe, bool enable);
 bool intel_set_pch_fifo_underrun_reporting(struct drm_device *dev,
 					   enum transcoder pch_transcoder,
 					   bool enable);
+void i9xx_check_fifo_underruns(struct drm_device *dev);
+bool __cpu_fifo_underrun_reporting_enabled(struct drm_device *dev,
+					   enum pipe pipe);
+
+/* i915_irq.c */
 void gen5_enable_gt_irq(struct drm_i915_private *dev_priv, uint32_t mask);
 void gen5_disable_gt_irq(struct drm_i915_private *dev_priv, uint32_t mask);
 void gen6_enable_pm_irq(struct drm_i915_private *dev_priv, uint32_t mask);
@@ -779,7 +784,6 @@
 }
 
 int intel_get_crtc_scanline(struct intel_crtc *crtc);
-void i9xx_check_fifo_underruns(struct drm_device *dev);
 void gen8_irq_power_well_post_enable(struct drm_i915_private *dev_priv);
 
 /* intel_crt.c */