Revert "gpu: ion: Don't issue kernel WARNING for iommu_map failure"

This reverts commit 4b63eaf2bbf3ee3265fd7081fbff619fe1232a90.
Revert "mdp4_overlay: Conditionally call ion_unmap_iommu()"

This reverts commit 58f36c0011669ad2c44785314609d0a8f979be99.
Revert "mdp4_overlay: Make sure ion_map_iommu() is successful for all domains all the time"

This reverts commit 056cce7cdbf3f0a46ab319e44b8a2c492d93d6ae.
Revert "mdp4_overlay: Fix graphical glitches caused by iommu mapping"

This reverts commit 93feda4c3cb2b921d1786b042928bc79a3ddf38b.