drm/i915: fix non-Ironlake 965 class crashes

My PIPE_CONTROL fix (just sent via Eric's tree) was buggy; I was testing a whole set of patches together and missed a conversion to the new HAS_PIPE_CONTROL macro, which will cause breakage on non-Ironlake 965 class chips. Fortunately, the fix is trivial and has been tested.

Be sure to use the HAS_PIPE_CONTROL macro in i915_get_gem_seqno, or we'll end up reading the wrong graphics memory, likely causing hangs, crashes, or worse.

index 7f52cc1..ef3d91d 100644
@@ -1793,7 +1793,7 @@ i915_get_gem_seqno(struct drm_device *dev)
 {
 	drm_i915_private_t *dev_priv = dev->dev_private;
 
-	if (IS_I965G(dev))
+	if (HAS_PIPE_CONTROL(dev))
 		return ((volatile u32 *)(dev_priv->seqno_page))[0];
 	else
 		return READ_HWSP(dev_priv, I915_GEM_HWS_INDEX);