mmc: fsl_esdhc_imx: drop useless code

Dropped useless code for i.MX eSDHC driver.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Tested-by: Steffen Dirkwinkel <s.dirkwinkel@beckhoff.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Martyn Welch <martyn.welch@collabora.com>
Reviewed-by: Lukasz Majewski <lukma@denx.de>