enable bus mastering on i915 at resume time

On 9xx chips, bus mastering needs to be enabled at resume time for much of the
chip to function.  With this patch, vblank interrupts will work as expected
on resume, along with other chip functions.   Fixes kernel bugzilla #10844.
Signed-off-by: NJie Luo <clotho67@gmail.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/drm/i915_drv.c

@@ -389,6 +389,7 @@ static int i915_resume(struct drm_device *dev)
 	pci_restore_state(dev->pdev);
 	if (pci_enable_device(dev->pdev))
 		return -1;
+	pci_set_master(dev->pdev);
 
 	pci_write_config_byte(dev->pdev, LBB, dev_priv->saveLBB);