Partially revert "drm/i915: Use full atomic modeset."

This partially reverts commit 74c090b1bdc57b1c9f1361908cca5a3d8a80fb08.

The DRIVER_ATOMIC cap cannot yet be exported because i915 lacks async
support.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 6e03e11..ce3bd0c 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1726,7 +1726,7 @@
 	 * to the atomic ioctl and the atomic properties.  Only plane operations on
 	 * a single CRTC will actually work.
 	 */
-	if (driver.driver_features & DRIVER_MODESET)
+	if (i915.nuclear_pageflip)
 		driver.driver_features |= DRIVER_ATOMIC;
 
 	return drm_pci_init(&driver, &i915_pci_driver);