of/platform: teardown DMA mappings on device destruction

Now that we can create and attach to IOMMU domains via of_dma_configure,
make sure we give the architecture a chance to tear them down when a
platform or amba device is destroyed.

Acked-by: Rob Herring <robh@kernel.org>
Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

diff --cc drivers/of/platform.c
Simple merge