staging: hikey9xx: hisilicon, hi6421-spmi-pmic.yaml: simplify props

As all regulator-specific properties got moved to be part of the
driver, remove them from the DT spec.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/2c2d09e332afa6539e5e80d69b23622941fd3d3e.1611212783.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>