regulator: mt6358: Use linear voltage helpers for single range regulators

Some of the regulators on the MT6358/MT6366 PMICs have just one linear
voltage range. These are the bulk regulators and VSRAM_* LDOs. Currently
they are modeled with one linear range, but also have their minimum,
maximum, and step voltage described.

Convert them to the linear voltage helpers. These helpers are a bit
simpler, and we can also drop the linear range definitions. Also reflow
the touched lines now that they are shorter.
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20230609083009.2822259-7-wenst@chromium.orgSigned-off-by: Mark Brown <broonie@kernel.org>