regulator: tps6507x: allow driver to use DEFDCDC{2,3}_HIGH register

Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

In TPS6507x, depending on the status of DEFDCDC{2,3} pin either
DEFDCDC{2,3}_LOW or DEFDCDC{2,3}_HIGH register needs to be read or
programmed to change the output voltage.

The current driver assumes DEFDCDC{2,3} pins are always tied low
and thus operates only on DEFDCDC{2,3}_LOW register. This need
not always be the case (as is found on OMAP-L138 EVM).

Unfortunately, software cannot read the status of DEFDCDC{2,3} pins.
So, this information is passed through platform data depending on
how the board is wired.

Signed-off-by: Anuj Aggarwal <anuj.aggarwal@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>