[telemetry] Change WinRing0 calling convention.

To fix the Windows XP perf bots specifically.

BUG=336558
TEST=None.
TBR=tonyg
NOTRY=True

Review URL: https://codereview.chromium.org/537213004

Cr-Commit-Position: refs/heads/master@{#293284}

tools/telemetry/telemetry/core/platform/power_monitor/msr_power_monitor.py

@@ -72,7 +72,7 @@ def WinRing0Path():
 def _Initialize():
   global _winring0
   if not _winring0:
-    winring0 = ctypes.CDLL(WinRing0Path())
+    winring0 = ctypes.WinDLL(WinRing0Path())
     if not winring0.InitializeOls():
       winring0_status = winring0.GetDllStatus()
       raise WinRing0Error(winring0_status,