drm/i915/gen9: Don't try to load garbage dmc firmware on resume

We need to make sure we don't put garbage into the hw if dmc firmware
loading failed mid-thru.

Cc: Damien Lespiau <damien.lespiau@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Sunil Kamath <sunil.kamath@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Tested-by: Daniel Stone <daniels@collabora.com> # SKL
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446069547-24760-8-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/intel_csr.c

@@ -223,7 +223,7 @@ void intel_csr_load_program(struct drm_device *dev)
 	 * Unfortunately the ACPI subsystem doesn't yet give us a way to
 	 * differentiate this, hence figure it out with this hack.
 	 */
-	if (I915_READ(CSR_PROGRAM(0)))
+	if ((!dev_priv->csr.dmc_payload) || I915_READ(CSR_PROGRAM(0)))
 		return;
 
 	fw_size = dev_priv->csr.dmc_fw_size;