ARM: dts: imx53-qsb: SDHC1 does not have cd-gpios

SDHC1 does not have any GPIO for reading the card detection status, so
remove 'cd-gpios'.

After this change card detection works via the internal SD controller mechanism.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>