soc: mediatek: cmdq: remove OR opertaion from err return

Debugging gets harder if we OR two error return values.
Return each error on it's own instead

Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
[mb: rephrase commit message]
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>