drm/i915: Add gen8_de_pipe_fault_mask()

Reduce the clutter a bit by introducing gen8_de_pipe_fault_mask().
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190626180344.26314-2-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/i915_irq.c

@@ -2844,6 +2844,14 @@ static u32 gen8_de_port_aux_mask(struct drm_i915_private *dev_priv)
 	return mask;
 }
 
+static u32 gen8_de_pipe_fault_mask(struct drm_i915_private *dev_priv)
+{
+	if (INTEL_GEN(dev_priv) >= 9)
+		return GEN9_DE_PIPE_IRQ_FAULT_ERRORS;
+	else
+		return GEN8_DE_PIPE_IRQ_FAULT_ERRORS;
+}
+
 static irqreturn_t
 gen8_de_irq_handler(struct drm_i915_private *dev_priv, u32 master_ctl)
 {
@@ -2956,12 +2964,7 @@ gen8_de_irq_handler(struct drm_i915_private *dev_priv, u32 master_ctl)
 		if (iir & GEN8_PIPE_FIFO_UNDERRUN)
 			intel_cpu_fifo_underrun_irq_handler(dev_priv, pipe);
 
-		fault_errors = iir;
-		if (INTEL_GEN(dev_priv) >= 9)
-			fault_errors &= GEN9_DE_PIPE_IRQ_FAULT_ERRORS;
-		else
-			fault_errors &= GEN8_DE_PIPE_IRQ_FAULT_ERRORS;
-
+		fault_errors = iir & gen8_de_pipe_fault_mask(dev_priv);
 		if (fault_errors)
 			DRM_ERROR("Fault errors on pipe %c: 0x%08x\n",
 				  pipe_name(pipe),