add config symbols for arch_{setup,teardown}_dma_ops

From: Christoph Hellwig
Date: Mon Feb 04 2019 - 03:14:34 EST

Hi all,

this series adds kconfig symbols to indicate that the architecture
provides the arch_setup_dma_ops and arch_teardown_dma_ops hooks.

This avoids polluting dma-mapping.h which is included by just about
every driver with implementation details, and also removes some