regulator: bd71837: Disable voltage monitoring for LDO3/4

There is a HW quirk in BD71837. The shutdown sequence timings for
bucks/LDOs which are enabled via register interface are changed.
At PMIC poweroff the voltage for BUCK6/7 is cut immediately at the
beginning of shut-down sequence. This causes LDO5/6 voltage
monitoring to detect under voltage and force PMIC to emergency
state instead of poweroff. Disable voltage monitoring for LDO5 and
LDO6 at probe to avoid this.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org