regulator: tps65023: Added support for the similiar TPS65020 chip

Defines a new voltage-table and allows registering of the tps65020 device.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>