regulator: s2mps11: Fix accidental enable of buck6 ramp delay

S2MPS11 supports enabling/disabling ramp delay only for buck[2346].
Other bucks have ramp delay enabled always.

However the bit shift for enabling buck6 ramp delay in register is equal
to 0. When ramp delay was set for the bucks unsupporting enable/disable
(buck[15789] and buck10), the ramp delay for buck6 was also enabled.

Fixes: b96244fad953 ("regulator: s2mps11: Don't check enable_shift before setting enable ramp rate")
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@linaro.org>