uboot-imx

mmc: use the generic error number

Use the generic error number instead of specific error number.
If use the generic error number, it can debug more easier.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Minkyu Kang <mk7.kang@samsung.com>