drivers: sdhc: imx_usdhc: add retry for DAT3 card detection

DAT3-based card detection can return a false negative on the first read
due to transient signal states after enabling detection. Add a bounded
retry loop (limited by IMX_USDHC_DAT3_DETECT_RETRY) with a short delay
between attempts to improve robustness.

Signed-off-by: Maochen Wang <maochen.wang@nxp.com>