zynq-zc702/devicetree: Add SD card detection back

Make sure that MIO0 is connected to the "CD" signal of the SD0 interface
in the XPS. Other things to check (they are missing in the ADI reference
design it seems):
SD0/CD = MIO 0
SD0/WP = MIO 15
I2C0/Reset = MIO 13
USB0/Reset = MIO 7
Enet0/Reset = MIO 11
QSPI/Feedback = MIO 8

Rebuild the FSBL after changing the design, to correctly pinmux this.