Revert "gpu: ion: delete ion_system_mapper.c"

This reverts commit d101885f58f5d068090bd6930c9cd8d27020dda2.
Revert "gpu: ion: several bugfixes and enhancements of ION"

This reverts commit 64c775e21e3917e235b1d344d3e70eafaae8aa18.
SmittyV