intel-agp: Set dma mask for i915

If DMAR is configured in but absent, we really do want to make sure that
the dma mask is set appropriately. Otherwise we get mapping failures on
highmem. Spotted by Zhenyu Wang.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/char/agp/intel-agp.c

@@ -1140,6 +1140,12 @@ static int intel_i915_configure(void)
 
 	intel_i9xx_setup_flush();
 
+#ifdef USE_PCI_DMA_API 
+	if (pci_set_dma_mask(intel_private.pcidev, DMA_BIT_MASK(36)))
+		dev_err(&intel_private.pcidev->dev,
+			"set gfx device dma mask 36bit failed!\n");
+#endif
+
 	return 0;
 }