ARM: davinci: da850: add pinctrl driver DT entries

For DT, DaVinci platform can use pinctrl-single driver for handling
padconf registers.

Enable PINCTRL Kconfig for MACH_DA8XX_DT platform. Add required
pinctrl DT entries in da850 dts file.

 Test procedure
  1)Populate DT file with NAND node information.
  2)Populate board DT file with pinmux information for NAND.
  3)Boot and confirm NAND is detected by the kernel.
  4)cat /proc/mtd to show partitions.

Signed-off-by: Kumar, Anil <anilkumar.v@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>