drm/i915: get the bridge device once.

The driver gets the bridge device in a number of places, upcoming
vga arb code paths need the bridge device, however they need it in
under a lock, and the pci lookup can allocate memory. So clean
this code up before then and get the bridge once for the driver lifetime.

Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -155,6 +155,7 @@ typedef struct drm_i915_private {
 
 	void __iomem *regs;
 
+	struct pci_dev *bridge_dev;
 	drm_i915_ring_buffer_t ring;
 
 	drm_dma_handle_t *status_page_dmah;