drm/i915/gt: Always flush the submission queue on checking for idle

We check for idle during debug prints and other debugging actions.
Simplify the flow by not touching execlists state.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210205174358.28465-1-chris@chris-wilson.co.ukSigned-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/gt/intel_engine_cs.c

@@ -1254,14 +1254,8 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
 		return true;
 
 	/* Waiting to drain ELSP? */
-	if (execlists_active(&engine->execlists)) {
-		synchronize_hardirq(to_pci_dev(engine->i915->drm.dev)->irq);
-
-		intel_engine_flush_submission(engine);
-
-		if (execlists_active(&engine->execlists))
-			return false;
-	}
+	synchronize_hardirq(to_pci_dev(engine->i915->drm.dev)->irq);
+	intel_engine_flush_submission(engine);
 
 	/* ELSP is empty, but there are ready requests? E.g. after reset */
 	if (!RB_EMPTY_ROOT(&engine->execlists.queue.rb_root))