regulator: s2mps11: Fix steps for buck7, buck8 and LDO35

LDO35 uses 25 mV step, not 50 mV.  Bucks 7 and 8 use 12.5 mV step
instead of 6.25 mV.  Wrong step caused over-voltage (LDO35) or
under-voltage (buck7 and 8) if regulators were used (e.g. on Exynos5420
Arndale Octa board).

Cc: <stable@vger.kernel.org>
Fixes: cb74685e ("regulator: s2mps11: Add samsung s2mps11 regulator driver")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>