regulator: pca9450: Enable DVS control via PMIC_STBY_REQ

When DVS is enabled via the devicetree properties
"nxp,dvs-run-voltage" and "nxp,dvs-standby-voltage" then
also the bit that enables DVS control via PMIC_STBY_REQ pin
should be set.

Signed-off-by: Rickard x Andersson <rickaran@axis.com>
Link: https://lore.kernel.org/r/20220429072211.24957-5-rickaran@axis.com
Signed-off-by: Mark Brown <broonie@kernel.org>