regulator: s2mps11: Don't check enable_shift before setting enable ramp rate

Current code misses updating the register when enable_shift is 0.
e.g. S2MPS11_BUCK9_RAMP_SHIFT and S2MPS11_BUCK6_RAMP_EN_SHIFT are 0.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>