PM of 6410

Prepare:
6410真正做DVFS和SLEEP是需要硬件支持的：
在sleep模式下VCCARM，VCCINT,VCCPLL是shutdown的。
SLEEP mode disconnects the internal power. Therefore, the power consumption due to CPU and the internal logic except the wakeup logic will be zero. In order to use the SLEEP mode two independent power sources are required. One of the two power sources supplies the power for the wake-up logic. The other one supplies the other internal logic including CPU, and must be controlled in order to be turned