regmap: kunit: Add test cases for regmap_multi_reg_(read,write}()

Add test cases for regmap_multi_reg_read() and regmap_multi_reg_write().

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Link: https://patch.msgid.link/20240711055352.3411807-1-linux@roeck-us.net


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