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>
1 file changed