agp/intel: Fix typo in needs_ilk_vtd_wa()

In needs_ilk_vtd_wa(), we pass in the GPU device but compared it against
the ids for the mobile GPU and the mobile host bridge. That latter is
impossible and so likely was just a typo for the desktop GPU device id
(which is also buggy).

Fixes commit da88a5f7f7
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Wed Feb 13 09:31:53 2013 +0000

    drm/i915: Disable WC PTE updates to w/a buggy IOMMU on ILK

Reported-by: Ting-Wei Lan <lantw44@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91127
References: https://bugzilla.freedesktop.org/show_bug.cgi?id=60391
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/char/agp/intel-gtt.c

@@ -581,7 +581,7 @@ static inline int needs_ilk_vtd_wa(void)
 	/* Query intel_iommu to see if we need the workaround. Presumably that
 	 * was loaded first.
 	 */
-	if ((gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_HB ||
+	if ((gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_D_IG ||
 	     gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_IG) &&
 	     intel_iommu_gfx_mapped)
 		return 1;