drm/i915: Sparse warns about the incorrect sign for storing bit17

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_drv.h

@@ -739,7 +739,7 @@ struct drm_i915_gem_object {
 	uint32_t stride;
 
 	/** Record of address bit 17 of each page at last unbind. */
-	long *bit_17;
+	unsigned long *bit_17;
 
 	/** AGP mapping type (AGP_USER_MEMORY or AGP_USER_CACHED_MEMORY */
 	uint32_t agp_type;