PMU: Prevent sleep modes from corrupting type state

[hannobraun]

When entering deep-sleep or power-down mode, the PDAWAKECFG register determines which peripherals will be enabled after the system wakes up. If this configuration doesn't match the enabled peripherals before entering the power-down mode, this will corrupt the type state. This means the type state on the peripheral APIs would no longer match the state of the actual peripherals. The respective methods are currently unsafe, for that reason.

I don't have a detailed design in mind, but the following should work:

• Add type state somewhere to represent PDAWAKECFG.
• When entering one of the affected low-power modes, have the method take ownership of the affected peripherals.
• After the system wakes up, return the peripherals from the method again, with a state matching PDAWAKECFG.