iommu/mediatek: Fix error code in probe()

This error path is supposed to return -EINVAL.  It used to return
directly but we added some clean up and accidentally removed the
error code.  Also I fixed a typo in the error message.

Fixes: c0b57581 ("iommu/mediatek: Add power-domain operation")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Yong Wu <yong.wu@mediatek.com>
Link: https://lore.kernel.org/r/YB0+GU5akSdu29Vu@mwanda


Signed-off-by: Joerg Roedel <jroedel@suse.de>