TPS65910: Add tps65910 regulator driver

The regulator module consists of 3 DCDCs and 8 LDOs. The output
voltages are configurable and are meant to supply power to the
main processor and other components

Signed-off-by: Graeme Gregory <gg@slimlogic.co.uk>
Signed-off-by: Jorge Eduardo Candelaria <jedu@slimlogic.co.uk>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>