regulator: mpq7920: Remove unneeded fields from struct mpq7920_regulator_info

Both *dev and *rdev are only used in .probe, so use local variable instead.
Also remove mpq7920_regulator_register() because it is so trivial and
there is only one caller.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20200114124449.28408-1-axel.lin@ingics.com


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