ARM: dts: AM33XX: Add NAND flash device tree data to am335x-evm

GPMC controller on AM335x-EVM has a NAND flash connected to it.
This patch updates following in am335x-evm.dts:
- adds nandflash specific pin-mux configs
- adds nand node as child of GPMC contoller, with information about
  NAND flash interface, NAND partition table, ECC scheme, elm handle id.
- updates GPMC node for newer GPMC DT properties added in linux-3.10.

Signed-off-by: Philip Avinash <avinashphilip@ti.com>
Signed-off-by: Gupta, Pekon <pekon@ti.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>