mfd: sec-core: Rename MFD and regulator names differently

Currently S2MPSXX multifunction device is named as *-pmic,
and these MFDs also supports regulator as a one of its MFD cell which
has the same name, because current name is confusing and we want to
sort it out.

We did discussed different approaches about how the MFD and it
cells need to be named here [1].
Based in the discussion this patch rename MFD regulator name as
*-regulator instead of current *-pmic.

This patch also changes the corresponding entries in the regulator driver
to keep git-bisect happy.

[1]-> https://lkml.org/lkml/2015/10/28/417



Suggested-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>