ARM: dts: mx23: add gpmi nand support

Add DT node for gpmi nand.
Also add pinctrl for gpmi nand.

Enable the gpmi-nand in mx23-evk board.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>