Pull dma-mapping update from Marek Szyprowski:
 "Provide the dma write coherent api (available previously on ARM
  architecture) for all other architectures, which use dma_ops-based dma
  mapping implementation.

  This lets one to use the same code in the device drivers regardless of
  the selected architecture"

* 'for-v3.18' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping:
  dma-mapping: Provide write-combine allocations
  s390: Implement dma_{alloc,free}_attrs()