mmc: fsl_esdhc_imx: enlarge mmc timeout

Flash system partition with fastboot will earse the partition firstly
The 600ms timeout will fail on some SD Card. Enlarge it to 5s to make
it works for most of sdcard

Cc: guoyin.chen <guoyin.chen@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>