ARM: davinci: da850 evm: add GPIO pinumux entries DT node

Add GPIO DT node and pinmux entries for DA850 EVM. GPIO is
configurable differently on different boards. So add GPIO
pinmuxing in dts file.

Signed-off-by: KV Sujith <sujithkv@ti.com>
Signed-off-by: Philip Avinash <avinashphilip@ti.com>
Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>