Provide a simple, 16 bit only, RAM backed regmap which supports raw I/O for
use in testing.
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230610-regcache-raw-kunit-v1-1-583112cd28ac@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>