If /sys/class/wakeup is available, get both kernel and native wakelock
stats from SystemSuspend, else we get native wakelock stats from
SystemSuspend and fallback to /d/wakeup_sources for kernel wakelock
stats.
Bug: 128923994
Test: atest FrameworksCoreTests:KernelWakelockReaderTest
Test: Compare dumpsys suspend_control against
dumpsys batterystats --checkin | grep kwl
to verify BatteryStats is getting wakelock stats
from SystemSuspend.
Change-Id: I08e56c984b903285bb965dd853dae4a63fdeb824
eedacc3221