regulator: tps65132: add regulator driver for TI TPS65132

Add regulator driver for the device TI TPS65132 which is single
inductor - dual output power supply device. TPS65132 device is
designed to support general positive/negative driven applications
like TFT display panels.

TPS65132 regulator driver supports to enable/disable and set voltage
on its output.

Signed-off-by: Venkat Reddy Talla <vreddytalla@nvidia.com>
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>