serial: uartps: Change logic how console_port is setup

Change logic how console_port is setup by using CON_ENABLED flag
instead of index. There will be unique cdns_uart_console() structures
that's why code can't use id for console_port assignment.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>