regulator: rk8xx: Return correct voltage for buck converters

regulator: rk8xx: Return correct voltage for buck converters

Information from the first range group is always used to calculate the
voltage returned for buck converters. This may result in wrong voltage
reported back to the regulator_get_value caller.

Traverse all the possible BUCK ranges to fix this issue.

Fixes: addd062beacc ("power: pmic: rk816: support rk816 pmic")
Fixes: b62280745e55 ("power: pmic: rk805: support rk805 pmic")
Fixes: b4a35574b38d ("power: pmic: rk817: support rk817 pmic")
Fixes: ee30068fa574 ("power: pmic: rk809: support rk809 pmic")
Signed-off-by: Joseph Chen <chenjh@rock-chips.com>
[jonas@kwiboo.se: fix checkpatch error, simplify buck get_value, update commit message]
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>