default or selected kernelversion does not have config value CONFIG_IBM_EMAC_FGAP.
Result is shown for kernelversion 5.4.123

Frame gap

configname: CONFIG_IBM_EMAC_FGAP

Linux Kernel Configuration
└─>Networking support
└─>Ethernet (10 or 100Mbit)
└─>Frame gap
In linux kernel since version 2.6.12