drm/i915/huc: Use helper function while waiting for DMA completion

Waiting for DMA status register can be done with dedicated function.
Lets use it as additional bonus will be smaller driver footprint.
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171024105056.43276-1-michal.wajdeczko@intel.com

drivers/gpu/drm/i915/intel_huc.c

@@ -151,7 +151,7 @@ static int huc_ucode_xfer(struct intel_uc_fw *huc_fw, struct i915_vma *vma)
 	I915_WRITE(DMA_CTRL, _MASKED_BIT_ENABLE(HUC_UKERNEL | START_DMA));
 
 	/* Wait for DMA to finish */
-	ret = wait_for((I915_READ(DMA_CTRL) & START_DMA) == 0, 100);
+	ret = intel_wait_for_register_fw(dev_priv, DMA_CTRL, START_DMA, 0, 100);
 
 	DRM_DEBUG_DRIVER("HuC DMA transfer wait over with ret %d\n", ret);