CONFIG_BOARD_MRMT_BL_PWM is not available for thedefaultarchitecture x86.
Result is shown for architecture avr32
default or selected kernelversion does not have config value CONFIG_BOARD_MRMT_BL_PWM.
Result is shown for kernelversion 6.5.1

Use PWM control for LCD Backlight

configname: CONFIG_BOARD_MRMT_BL_PWM

Linux Kernel Configuration
└─>Use PWM control for LCD Backlight
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  
Use PWM driver for controlling LCD Backlight.
Otherwise, LCD Backlight is always on.