regmap: Make use of get_unaligned_be24(), put_unaligned_be24()

Since we have a proper endianness converters for BE 24-bit data use
them. While at it, format the code using switch-cases as it's done
for the rest of the endianness handlers.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220726151213.71712-1-andriy.shevchenko@linux.intel.com


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