serial: sirf: assign console default index if users not set a valid one

it seems this is a more typical behaviour from reviewing other console
drivers.
Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sirfsoc_uart.c

@@ -1236,7 +1236,7 @@ sirfsoc_uart_console_setup(struct console *co, char *options)
 	struct sirfsoc_uart_port *sirfport;
 	struct sirfsoc_register *ureg;
 	if (co->index < 0 || co->index >= SIRFSOC_UART_NR)
-		return -EINVAL;
+		co->index = 1;
 	sirfport = sirf_ports[co->index];
 	if (!sirfport)
 		return -ENODEV;