iommu/mediatek: Add mutex for m4u_group and m4u_dom in data

Add a mutex to protect the data in the structure mtk_iommu_data,
like ->"m4u_group" ->"m4u_dom". For the internal data, we should
protect it in ourselves driver. Add a mutex for this.
This could be a fix for the multi-groups support.

Fixes: c3045f39 ("iommu/mediatek: Support for multi domains")
Signed-off-by: Yunfei Wang <yf.wang@mediatek.com>
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/20220503071427.2285-8-yong.wu@mediatek.com


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