[coreboot] how to route IRQ4 (COM1) on LPC bus for bayleybay_fsp

[benoit]

Yep,

I think it should be great to have these options available in Kconfig.
SETUPSERIQ should be transform to CONFIG_SETUPSERIQ.
CONFIG_SERIRQ_CONTINUOUS_MODE is very important when SERIRQ is activated
to avoid spurious interrupt and other mysterious LPC IRQ issues.

Thanks
Benoit