User UART3 on HiKey board.
User UART3 on HiKey board.

This is more commonly used for firmware and kernel logs and, more
importantly, is easier to access thanks to the mezzanine board.

Change-Id: I076aefc3f66b8de85081a3fd1cf69acef671b6f0

project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification