default or selected kernelversion does not have config value CONFIG_SERIAL_BFIN_SPORT0_UART_CTSRTS.
Result is shown for kernelversion 6.7-rc3

Enable UART over SPORT0 hardware flow control

configname: CONFIG_SERIAL_BFIN_SPORT0_UART_CTSRTS

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>Serial drivers
└─>Enable UART over SPORT0 hardware flow control
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
Enable hardware flow control in the driver.