TI Palmas series Power Management IC have multiple pins which can be
configured for different functionality. This pins can be configured
for different function. Also their properties like pull up/down,
open drain enable/disable are configurable.

Add support for pincontrol driver Palmas series device like TPS65913,
TPS80036. The driver supports to be register from DT only.

Changes from V1:
- Add generic property for pins and functions in pinconf-generic.
- Add APIs to map the DT and subnode.
- Move common utils APIs to the pinctrl-utils from this file.
- Update the binding document accordingly.
Changes from V2:
- Add ack by Lee.
- Correct the binding docs.
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>