graphics_Idle: add mt8192 devfreq path

On asurada, gpu path is: /sys/devices/platform/soc/13000000.mali

BUG=b:176270331
TEST=pass graphics_Idle on asurada

Change-Id: I02236756a0bf9a3d2c77b08f1479d9be61d0efd7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2603056
Commit-Queue: Nicolas Boichat <drinkcat@chromium.org>
Commit-Queue: Hsin-Yi Wang <hsinyi@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Auto-Submit: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Hsin-Yi Wang <hsinyi@chromium.org>
diff --git a/client/site_tests/graphics_Idle/graphics_Idle.py b/client/site_tests/graphics_Idle/graphics_Idle.py
index 6207941..8dff479 100755
--- a/client/site_tests/graphics_Idle/graphics_Idle.py
+++ b/client/site_tests/graphics_Idle/graphics_Idle.py
@@ -226,6 +226,7 @@
         mt8173_node = '/sys/devices/soc/13000000.mfgsys-gpu/'
         mt8173_419_node = '/sys/devices/platform/soc/13000000.mfgsys-gpu/'
         mt8183_node = '/sys/devices/platform/soc/13040000.mali/'
+        mt8192_node = '/sys/devices/platform/soc/13000000.mali/'
 
         if self._cpu_type == 'exynos5':
             if os.path.isdir(exynos_node):
@@ -261,6 +262,9 @@
             elif os.path.isdir(mt8183_node):
                 node = mt8183_node
                 use_devfreq = True
+            elif os.path.isdir(mt8192_node):
+                node = mt8192_node
+                use_devfreq = True
             else:
                 logging.error('Error: unknown mediatek SoC.')
                 return self.handle_error('Unknown mediatek SoC.')