Introduce a new GUID Hob gEarly16550UartBaseAddressGuid to cache the base address of the 16550 UART, for when PCD access is not available. Signed-off-by: Sami Mujawar <sami.mujawar@arm.com> Reviewed-by: Ard Biesheuvel <Ard.Biesheuvel@arm.com> Acked-by: Laszlo Ersek <lersek@redhat.com>