ARM: dts: imx50-evk: Fix the chip select 1 IOMUX

ARM: dts: imx50-evk: Fix the chip select 1 IOMUX

The SPI chip selects are represented as:

cs-gpios = <&gpio4 11 GPIO_ACTIVE_LOW>, <&gpio4 13 GPIO_ACTIVE_LOW>;

, which means that they are used in GPIO function instead of native
SPI mode.

Fix the IOMUX for the chip select 1 to use GPIO4_13 instead of
the native CSPI_SSI function.

Fixes: c605cbf5e135 ("ARM: dts: imx: add device tree support for Freescale imx50evk board")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>