This commit adds minimal support of Xen hypervisor console via UART-like
driver. Implementation allows to use poll_in/poll_out char interface for
uart_console.c driver directly to HV console instead of using Xen
virtual PL011 UART. Future implementation will support interrupt driven
interface on Xen event channels, currently it is under development.
Also this commit introduces early console_io Xen interface, which allows
to receive printk/stdout messages quickly after start, but requires Xen,
built with CONFIG_DEBUG option.
Signed-off-by: Dmytro Firsov <dmytro_firsov@epam.com>
d9a3efb834