CONFIG_MMU_SUN3 is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

CONFIG_MMU_SUN3 (not configurable)

modulename: sun3kmap.ko

and/or

ints.ko

configname: CONFIG_MMU_SUN3

Linux/68k Kernel Configuration
└─>Platform dependent setup
└─>MMU_SUN3
In linux kernel since version 2.6.12  
source code:
arch/m68k/mm/
depends
 or CONFIG_MMU |
NOT | CONFIG_MMU_COLDFIRE or  NOT CONFIG_MMU_MOTOROLA

is selected by
CONFIG_Q40
CONFIG_M68060

is depended by
CONFIG_SUN3