CONFIG_M68020 is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

68020 support

configname: CONFIG_M68020

Linux/68k Kernel Configuration
└─>Platform dependent setup
└─>68020 support
In linux kernel since version 2.6.12  
If you anticipate running this kernel on a computer with a MC68020
processor, say Y. Otherwise, say N. Note that the 68020 requires a
68851 MMU (Memory Management Unit) to run Linux/m68k, except on the
Sun 3, which provides its own version.