mmc: mxs-mmc: fix error return code in mxs_mmc_probe()

Fix to return -ENODEV in the request dma error case instead
of 0, as done elsewhere in this function.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Chris Ball <cjb@laptop.org>