drm/i915/pmu: Skip sampling engines with no enabled counters

As we have more and more engines do not waste time sampling the ones no-
one is monitoring.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230519154946.3751971-4-umesh.nerlige.ramappa@intel.com

drivers/gpu/drm/i915/i915_pmu.c

@@ -350,6 +350,9 @@ engines_sample(struct intel_gt *gt, unsigned int period_ns)
 		return;
 
 	for_each_engine(engine, gt, id) {
+		if (!engine->pmu.enable)
+			continue;
+
 		if (!intel_engine_pm_get_if_awake(engine))
 			continue;