drm/i915: Fix incorrect intel_ring_begin size in BSD ringbuffer.

The ring_begin API was taking a number of bytes, while all of our
other begin/end macros take number of dwords.  Change the API over to
dwords to prevent future bugs.

Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 9ed8ecd..f3f681f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1075,7 +1075,7 @@
 	drm_i915_private_t *dev_priv = dev->dev_private;                \
 	if (I915_VERBOSE)						\
 		DRM_DEBUG("   BEGIN_LP_RING %x\n", (int)(n));		\
-	intel_ring_begin(dev, &dev_priv->render_ring, 4*(n));		\
+	intel_ring_begin(dev, &dev_priv->render_ring, (n));		\
 } while (0)