regulator: max77826: Remove erroneous additionalProperties

In this particular location additionalProperties actually declares a property
named `additionalProperties` instead of specifying there should be no other
properties.

Signed-off-by: Iskren Chernev <iskren.chernev@gmail.com>
Link: https://lore.kernel.org/r/20200425125335.2674534-1-iskren.chernev@gmail.com


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