ARM: dts: imx53-qsb: Describe the esdhc1 card detect pin

The micro SD card slot uses GPIO3_13 as card detect pin, so describe
it in the devicetree.

This was noticed when converting imx53-qsb board to driver model
in U-Boot as the micro SD card was not getting detected.

After this change it is possible to load the dtb and zImage
from the SD card and boot Linux.

Signed-off-by: Fabio Estevam <festevam@gmail.com>