pmic: pca9450: permit config on all bucks and LDOs

In order to have the possibility to configure the regulators at system
startup through DM support, all LDOs and bucks must be able to be
changeable. Currently there is a limitation to change the values when
the output is enabled. Since the driver is based on the ROHM BD71837 and a
comment that describes a limitation about switching while the output is
enabled can also be found there, the limitation probably comes from this type.

Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>