Fix ULPI low power mode entry with USB disconnected.
Fix ULPI low power mode entry with USB disconnected.

* fixes #1408

kwagyeman/openmv,openmv/openmv,iabdalkader/openmv,kwagyeman/openmv,iabdalkader/openmv,openmv/openmv,iabdalkader/openmv,kwagyeman/openmv,iabdalkader/openmv,openmv/openmv,kwagyeman/openmv,openmv/openmv