amdsbwd: always enable watchdog register decoding

This seems to be required even if the watchdog is accessed via the common
MMIO space.

Tested on:

• Ryzen 3 3200U APU;
• Ryzen 7 5800X CPU with X570 chipset.

(cherry picked from commit cca0d3bbd8c9f8b50c6940c33704a6c8c464b68f)