regmap: kunit: Add cache-drop test with multiple cache blocks

regmap: kunit: Add cache-drop test with multiple cache blocks

Add a test case for dropping only some cache blocks and leaving others
unchanged.

The regmap is divided into 8 register ranges, and only 4 of these are
written with values. This creates 4 non-contiguous ranges of registers
with cached values.

One whole range is then dropped, and part of another range. A cache
sync is then performed to check that the correct registers were written,
and the correct values were written to these registers.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://msgid.link/r/20240408144600.230848-11-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>