powerstats: update MRR refresh rate residency node path

Refresh rate residency is not directly related to backlight state.
Relocate to a more appropriate location.

Bug: 315424658
Test: vts-tradefed run vts -m VtsHalPowerStatsTargetTest
Change-Id: Ia95cff1062045fa58544946bc525ea3678fd7836

powerstats/akita/service.cpp

@@ -37,7 +37,7 @@ using aidl::android::hardware::power::stats::PowerStatsEnergyConsumer;
 void addDisplay(std::shared_ptr<PowerStats> p) {
     // Add display residency stats
     struct stat buffer;
-    if (stat("/sys/class/backlight/panel0-backlight/time_in_state", &buffer)) {
+    if (stat("/sys/class/drm/card0/device/primary-panel/time_in_state", &buffer)) {
         // time_in_state doesn't exist
         std::vector<std::string> states = {
             "Off",