default or selected kernelversion does not have config value CONFIG_SERIAL_EFM32_UART_CONSOLE.
Result is shown for kernelversion 6.9.9

EFM32 UART/USART console support

configname: CONFIG_SERIAL_EFM32_UART_CONSOLE

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>Serial drivers
└─>EFM32 UART/USART console support
In linux kernel since version 3.1 (release Date: 2011-10-24)