MMC: S3C24XX: Update error debugging.

Add better debugging to show where errors are being
generated, as some error codes can come from several
different code paths.

Also fix the error return path from s3cmci_setup_data()
to return the error it returned to the request.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>