drm/i915: Removed duplicate members from submit_request

Where there were duplicate variables for the tail, context and ring (engine)
in the gem request and the execlist queue item, use the one from the request
and remove the duplicate from the execlist queue item.

Issue: VIZ-4274

v1: Rebase
v2: Fixed build issues. Keep separate postfix & tail pointers as these are
used in different ways. Reinserted missing full tail pointer update.

Signed-off-by: Nick Hoath <nicholas.hoath@intel.com>
Reviewed-by: Thomas Daniel <thomas.daniel@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_lrc.h

@@ -105,10 +105,6 @@ u32 intel_execlists_ctx_id(struct drm_i915_gem_object *ctx_obj);
  * All accesses to the queue are mediated by a spinlock (ring->execlist_lock).
  */
 struct intel_ctx_submit_request {
-	struct intel_context *ctx;
-	struct intel_engine_cs *ring;
-	u32 tail;
-
 	struct list_head execlist_link;
 
 	int elsp_submitted;