SANTVEND: LDO bypass feature

The internal ldo can be used to generate some internal supplies but it is also possible to set the voltage correctly in the PMIC and bypass the ldo completely, which is the preferred mode. These patches implements such bypass.

The feature is ported from Jethro BSP (linux-imx-4.5.15).

Without patches:

root@localhost:~# for i in $(find /sys -name "bypass"); do echo $(dirname $i); cat $(dirname $i)/name; cat $(dirname $i)/bypass; done
/sys/devices/platform/soc/2000000.bus/20c8000.anatop/20c8000.anatop:regulator-vddsoc/regulator/regulator.27
vddsoc
disabled
/sys/devices/platform/soc/2000000.bus/20c8000.anatop/20c8000.anatop:regulator-vddcore/regulator/regulator.25
vddarm
disabled
/sys/devices/platform/soc/2000000.bus/20c8000.anatop/20c8000.anatop:regulator-vddpu/regulator/regulator.26
vddpu
disabled
root@localhost:~#

With patches:

root@localhost:~# for i in $(find /sys -name "bypass"); do echo $(dirname $i); cat $(dirname $i)/name; cat $(dirname $i)/bypass; done
/sys/devices/platform/soc/2000000.bus/20c8000.anatop/20c8000.anatop:regulator-vddsoc/regulator/regulator.27
vddsoc
enabled
/sys/devices/platform/soc/2000000.bus/20c8000.anatop/20c8000.anatop:regulator-vddcore/regulator/regulator.25
vddarm
enabled
/sys/devices/platform/soc/2000000.bus/20c8000.anatop/20c8000.anatop:regulator-vddpu/regulator/regulator.26
vddpu
enabled
root@localhost:~#