regmap: kunit: Add test cases for regmap_read_bypassed()

This adds test cases to prove that regmap_read_bypassed() reads
the hardware value while the regmap is in cache-only.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://msgid.link/r/20240408144600.230848-12-rf@opensource.cirrus.com


Signed-off-by: Mark Brown <broonie@kernel.org>