misc: pmem: Squashed revert of DMA changes

Revert "pmem: Do not use special case for DMA."

This reverts commit cb1c16e11db36b8d4bdba9a8b90aff6636480126.

Revert "misc: pmem: Explictly mark DMA allocations as GFP_KERNEL"

This reverts commit f85cf2fbdcf73f156e01d5bb3d8105e3a14cc5b7.

Revert "misc: pmem: Manage DMA allocation failures"

This reverts commit b27b65c4104ebc1fa056db97929d0aacb7bfd913.

Revert "misc: pmem: Add support for CMA."

This reverts commit c0f9f27defba4b066e94a2f5ef390c713addcd9c.

Change-Id: I8a3f2f6ca813da8e0d99663653ce91e829655979