mmc: fsl_esdhc_imx: fix the DTOCV to 0xE

mmc: fsl_esdhc_imx: fix the DTOCV to 0xE

On imx6Q/imx6DL, we find if config the DTOCV to 0~3, it will impact
cmd6 behavior, after cmd6 get transfer complete interrupt, the data0
line will keep low over 5 seconds. This should be a IC bug on imx6Q/DL.
For other platforms, do not has this issue.

To fix this issue, fix the DTOCV to 0xE, the max setting, this also align
with Linux configuration.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>