drm/i915/skl+: don't trust IPC value set by BIOS

If KMS decide to disable IPC make sure we override IPC configuration set
by BIOS.

Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180824093225.12598-5-mahesh1.kumar@intel.com

drivers/gpu/drm/i915/intel_pm.c

@@ -6118,10 +6118,8 @@ void intel_enable_ipc(struct drm_i915_private *dev_priv)
 	u32 val;
 
 	/* Display WA #0477 WaDisableIPC: skl */
-	if (IS_SKYLAKE(dev_priv)) {
+	if (IS_SKYLAKE(dev_priv))
 		dev_priv->ipc_enabled = false;
-		return;
-	}
 
 	val = I915_READ(DISP_ARB_CTL2);