LiteUART serial port console support

configname: CONFIG_SERIAL_LITEUART_CONSOLE

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>Serial drivers
└─>LiteUART serial port console support
In linux kernel since version 5.2 (release Date: 2019-07-07)  
Say 'Y' or 'M' here if you wish to use the FPGA-based LiteUART serial
controller from LiteX SoC builder as the system console
(the system console is the device which receives all kernel messages
and warnings and which allows logins in single user mode).
Otherwise, say 'N'.