regulator: dt-bindings: pf8x00: fix nxp,phase-shift doc

nxp,phase-shift is an enum so use enum format to describe it.
Minimum and maximum values are also wrong.

Signed-off-by: Adrien Grassein <adrien.grassein@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210114174714.122561-3-adrien.grassein@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>