regulator: tps6507x: Remove unused min_uV and max_uV from struct tps_info

The min_uV and max_uV are not used in this driver.
For table based voltage mappings, we can get min_uV and max_uV by
info->table[0] and info->table[table_len -1].
Thus remove min_uV and max_uV from struct tps_info.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>