regulator: Update documentation after renaming function argument

Update documentation for regulator_register() function after renaming
its argument.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -3573,7 +3573,7 @@ static void rdev_init_debugfs(struct regulator_dev *rdev)
 /**
  * regulator_register - register regulator
  * @regulator_desc: regulator to register
- * @config: runtime configuration for regulator
+ * @cfg: runtime configuration for regulator
  *
  * Called by regulator drivers to register a regulator.
  * Returns a valid pointer to struct regulator_dev on success