The modpost script is not happy

  WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/base/regmap/regmap-spi.o

because there is a missing module description.

Add it to the module.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://msgid.link/r/20240410202912.1659275-3-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>