Revert "msm: iommu: re-use existing buffers for `extra' mappings"

This reverts commit b35a8f2d16b99c0ac0e30b3b8030ba4d45ea0479.
Revert "Revert "Revert "Revert "msm: msm_fb: Map RGB layers to the max possible size.""""

This reverts commit 7403481f7799dad879bd767ec27edb91f74e2cbd.
Revert "Revert "msm: msm_fb: Fix Regressions because of overmap changes.""

This reverts commit 19d2237edc9a3b866886e78576de45d200d4ffee.