Update instructions in IPowerManager.aidl.
Update instructions in IPowerManager.aidl.

Clarify IPowerManager.aidl's instructions for keeping the
C++ implementation in sync.

Change-Id: Ic51a3844483031e71fe2cfa1d3e8a065df86d119

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base