regulator: mcp16502: Remove setup_regulators function

It seems a little bit odd current code pass struct regulator_config rather
than a pointer to setup_regulators. The setup_regulators is so simple and
only has one caller, so remove it.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>