drm/i915/spt+: Don't reset invalid AUX channel interrupt bits in SDEIMR

The SDE interrupt bits 25, 26 and 27 are either reserved or meant for
DDI E hotplug in SPT+. These bits are meant for AUX channels only in LPT
and CPT, so add the appropriate checks.
Signed-off-by: NDhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170909004255.14827-1-dhinakaran.pandiyan@intel.com

drivers/gpu/drm/i915/i915_irq.c

@@ -3241,8 +3241,10 @@ static void ibx_irq_postinstall(struct drm_device *dev)
 
 	if (HAS_PCH_IBX(dev_priv))
 		mask = SDE_GMBUS | SDE_AUX_MASK | SDE_POISON;
-	else
+	else if (HAS_PCH_CPT(dev_priv) || HAS_PCH_LPT(dev_priv))
 		mask = SDE_GMBUS_CPT | SDE_AUX_MASK_CPT;
+	else
+		mask = SDE_GMBUS_CPT;
 
 	gen5_assert_iir_is_zero(dev_priv, SDEIIR);
 	I915_WRITE(SDEIMR, ~mask);