ARC: [nsimosci] Allow "headless" models to boot

There are certain test configuration of virtual platform which don't
have any real console device (uart/pgu). So add tty0 as a fallback console
device to allow system to boot and be accessible via telnet

Otherwise with ttyS0 as only console, but 8250 disabled in kernel build,
init chokes.

Reported-by: Anton Kolesov <akolesov@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: <stable@vger.kernel.org> #3.10, 3.12, 3.14, 3.16