Revert "serial: core: Use cons->index for preferred console registration"

This reverts commit 91daae03.

The origin patch is causing an issue on r8a7791/koelsch and
r8a7795/salvator-xs platforms where cons->index is not initialized to
expected value.
It is safer to revert this patch for now till it is clear why this is
happening.
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/59f51af6bb03fce823663764d17ad0291aa01ab2.1571222199.git.michal.simek@xilinx.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/serial_core.c

@@ -2832,8 +2832,7 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
 		lockdep_set_class(&uport->lock, &port_lock_key);
 	}
 	if (uport->cons && uport->dev)
-		of_console_check(uport->dev->of_node, uport->cons->name,
-				 uport->cons->index);
+		of_console_check(uport->dev->of_node, uport->cons->name, uport->line);
 
 	uart_configure_port(drv, state, uport);