The CD pin on SD2 socket is not connected by hardware, because this pin
is used as ALERT pin of PTN5110. So we have to use DAT3 for CD detection.

Since the USDHC driver does not support using DAT3 for CD, we have set this
port to non-removable in DTS. In SPL, we switch the pad setting of DAT3 for
CD detecting.

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>