CONFIG_MACH_PIC32 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

Microchip PIC32 Family

configname: CONFIG_MACH_PIC32

System type
└─>Microchip PIC32 Family
In linux kernel since version 4.1 (release Date: 2015-06-21)  
This enables support for the Microchip PIC32 family of platforms.

Microchip PIC32 is a family of general-purpose 32 bit MIPS core
microcontrollers.

is selected by
CONFIG_PIC32_DMT