[coreboot] How to enable ttyS0 on my board?

[김유석]

Dear Sir.

My own board is based on ADI SG-2440.

SG-2440 schematic is only connect(enable) the (UART1_RXD, UART1_TXD) to 
serial console port. So, only can use the "ttyS1" on kernel.

But i want to use the "ttyS0".

My board's schematic is a connect the uart0(UART0_RXD, UART0_TXD) and 
uart1(UART1_RXD, UART1_TXD) both.

But message only out the the uart1.

How can use/enable the uart0 on my board?

What source code need a modify?

Thank you.