regulator: tps51632: Ensure [base|max]_voltage_uV pdata settings are valid

If pdata->base_voltage_uV is missing or the settings of pdata->base_voltage_uV
and pdata->max_voltage_uV are out of range, TPS51632_VOLT_VSEL macro
returns wrong vsel.

Thus add checking [base|max]_voltage_uV pdata settings in probe.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>