Powerpc: eSDHC: Fix mmc read write err in uboot of T4240QDS board

Fill the right command type when using CMD12 to stop data transfer.

Signed-off-by: Haijun Zhang <Haijun.Zhang@freescale.com>
CC: Fleming Andrew-AFLEMING <AFLEMING@freescale.com>
CC: Scott Wood <scottwood@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>