EDAC, fsl_ddr: Fix error return code in fsl_mc_err_probe()

Return negative error code from the edac_mc_add_mc() error handling case
instead of 0, as done elsewhere in this function.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: York Sun <york.sun@nxp.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/1473350284-26482-1-git-send-email-weiyj.lk@gmail.com


Signed-off-by: Borislav Petkov <bp@suse.de>