Enable regmap build

configname: CONFIG_REGMAP_BUILD

Linux Kernel Configuration
└─>Device Drivers
└─>Generic Driver Options
└─>Enable regmap build
In linux kernel since version 4.14.327 (release Date: 2023-10-10)  
This option exists purely to allow the regmap KUnit tests to
be enabled without having to enable some driver that uses
regmap due to unfortunate issues with how KUnit tests are
normally enabled.

selects
CONFIG_REGMAP

depends
CONFIG_KUNIT