regulator: mtk-dvfsrc: Fix wrong dev pointer for devm_regulator_register

If use dev->parent, the regulator_unregister will not be called when this
driver is unloaded. Fix it by using dev instead.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20210702142140.2678130-1-axel.lin@ingics.com


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