serial: liteuart: Remove a copy of UART id in private structure

The struct liteuart_port keeps tracking of UART ID which is also
saved in the struct uart_port as line member. Drop the former one
and use the latter everywhere.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Gabriel Somlo <gsomlo@gmail.com>
Link: https://lore.kernel.org/r/20230123192604.81452-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>