regulator/lp3971: vol_map out of bounds in lp3971_{ldo,dcdc}_set_voltage()

After `for (val = LDO_VOL_MIN_IDX; val <= LDO_VOL_MAX_IDX; val++)', if no break
occurs, val reaches LDO_VOL_MIN_IDX + 1, which is out of bounds for
ldo45_voltage_map[] and ldo123_voltage_map[].

Similarly BUCK_TARGET_VOL_MAX_IDX + 1 is out of bounds for buck_voltage_map[].

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>