Port the scmi regulator driver to the new SCMI voltage interface based
on protocol handles and common devm_get_ops().

Link: https://lore.kernel.org/r/20210316124903.35011-30-cristian.marussi@arm.com
Cc: Mark Brown <broonie@kernel.org>
Tested-by: NFlorian Fainelli <f.fainelli@gmail.com>
Acked-by: NMark Brown <broonie@kernel.org>
Signed-off-by: NCristian Marussi <cristian.marussi@arm.com>
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>