Pull dma-mapping rename from Christoph Hellwig:
 "Move all the dma-mapping code to kernel/dma and lose their dma-*
  prefixes"

* tag 'dma-rename-4.18' of git://git.infradead.org/users/hch/dma-mapping:
  dma-mapping: move all DMA mapping code to kernel/dma
  dma-mapping: use obj-y instead of lib-y for generic dma ops