staging: regulator: hi6421v600-regulator: cleanup struct hisi_regulator

There are several fields on this struct that can be removed,
as they already exists at struct regulator_desc.

Remove them, cleaning up the code in the process.

While here, rename it to hi6421v600_regulator_info, in order
to better match the driver's name.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/648d48f11368a9869d760c2bd54bfbc3feb4f44c.1597647359.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>