ARM: mx28: Add SPI 2 pinmux into imx28.dtsi

Add this SSP port 2 pin multiplexing configuration into the imx28.dtsi file.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chris Ball <cjb@laptop.org>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>