mmc: sdhci: Read cd-gpio from devicetree

This patch reads cd-gpio property from devicetree

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>