doc/README.fsl-esdhc

CONFIG_SYS_FSL_ESDHC_LE means ESDHC IP is in little-endian mode.
CONFIG_SYS_FSL_ESDHC_BE means ESDHC IP is in big-endian mode.

Accessing ESDHC registers can be determined by ESDHC IP's endian
mode or processor's endian mode.