drm/i915: Reserve some priority bits for internal use

In the next few patches, we will want to give a small priority boost to
some requests/queues but not so much that we perturb the user controlled
order. As such we will shift the user priority bits higher leaving
ourselves a few low priority bits for our internal bumping.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181001123204.23982-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.h

@@ -3236,7 +3236,7 @@ int i915_gem_object_wait(struct drm_i915_gem_object *obj,
 int i915_gem_object_wait_priority(struct drm_i915_gem_object *obj,
 				  unsigned int flags,
 				  const struct i915_sched_attr *attr);
-#define I915_PRIORITY_DISPLAY I915_PRIORITY_MAX
+#define I915_PRIORITY_DISPLAY I915_USER_PRIORITY(I915_PRIORITY_MAX)
 
 int __must_check
 i915_gem_object_set_to_wc_domain(struct drm_i915_gem_object *obj, bool write);