gpio: davinci: DT changes for driver

- Add of_device_id for Davinci GPIO driver.
- Add function to populate data from DT.
- Modify the probe to read from DT if DT match is found.
- Add DT binding documentation for Davinci GPIO properties in a new file
  gpio-davinci.txt located at Documentation/devicetree/bindings/gpio/.

Signed-off-by: KV Sujith <sujithkv@ti.com>
Signed-off-by: Philip Avinash <avinashphilip@ti.com>
ARM: davinci: da850: add GPIO DT entries

Add DT entries for Davinci GPIO.

Signed-off-by: KV Sujith <sujithkv@ti.com>
Signed-off-by: Philip Avinash <avinashphilip@ti.com>
ARM: davinci: da850 evm: add GPIO DT data

- Add GPIO DT Data and pinmux for DA850 EVM. GPIO is configurable differently
  on different boards. So add GPIO pinmuxing in dts file.
- Dependency: This patch is dependent on Grab-pin-control patch;
  https://patchwork.kernel.org/patch/2013751/

Signed-off-by: KV Sujith <sujithkv@ti.com>
Signed-off-by: Philip Avinash <avinashphilip@ti.com>