Fix little_cpu_power collection.

Currently always getting 0, significantly undercounting cpu power at
least in some cases (e.g. I saw 1700 vs 4300 in fishdom)

Bug: b/284462263
Change-Id: Idd525f25cfc419a4a9d23a3fc99e938e99e1e715
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4672592
Auto-Submit: Roman Lavrov <romanl@google.com>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Roman Lavrov <romanl@google.com>

src/tests/restricted_traces/restricted_trace_perf.py

@@ -494,7 +494,7 @@ class GPUPowerStats():
             logging.debug('Checking line: %s' % line)
             if not line:
                 break
-            if "S2M_VDD_CPUCL0" in line:
+            if "S4M_VDD_CPUCL0" in line:
                 self.little_cpu_power = line.split()[1]
                 break
         logging.debug("self.little_cpu_power %s" % self.little_cpu_power)