spi: Extract spi_toggle_csgpiod() helper for better maintanance

The multi-CS support splits the comment and the code in the spi_set_cs().
To avoid this in the future extract spi_toggle_csgpiod() helper.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240415193340.1279360-2-andriy.shevchenko@linux.intel.com


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