regulator: rk8xx: Return correct voltage for switchout converters

regulator: rk8xx: Return correct voltage for switchout converters

The voltage value for switchout converters is always reported as 0 uV.
When the switch is enabled, it's voltage is same as input supply.

Fix this by implementing get_value for switchout converters.

Fixes: ee30068fa574 ("power: pmic: rk809: support rk809 pmic")
Signed-off-by: shengfei Xu <xsf@rock-chips.com>
[jonas@kwiboo.se: fix checkpatch error, update commit message]
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>