iommu/mediatek: Add power-domain operation

In the previous SoC, the M4U HW is in the EMI power domain which is
always on. the latest M4U is in the display power domain which may be
turned on/off, thus we have to add pm_runtime interface for it.

When the engine work, the engine always enable the power and clocks for
smi-larb/smi-common, then the M4U's power will always be powered on
automatically via the device link with smi-common.

Note: we don't enable the M4U power in iommu_map/unmap for tlb flush.
If its power already is on, of course it is ok. if the power is off,
the main tlb will be reset while M4U power on, thus the tlb flush while
m4u power off is unnecessary, just skip it.
Therefore, we increase the ref_count for pm when pm status is ACTIVE,
otherwise, skip it. Meanwhile, the tlb_flush_range is called so often,
thus, update pm ref_count while the SoC has power-domain to avoid touch the
dev->power.lock. and the tlb_flush_all only is called when boot, so no
need check if the SoC has power-domain to keep code clean.

There will be one case that pm runctime status is not expected when tlb
flush. After boot, the display may call dma_alloc_attrs before it call
pm_runtime_get(disp-dev), then the m4u's pm status is not active inside
the dma_alloc_attrs. Since it only happens after boot, the tlb is clean
at that time, I also think this is ok.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Link: https://lore.kernel.org/r/20210111111914.22211-21-yong.wu@mediatek.com
Signed-off-by: Will Deacon <will@kernel.org>