ANDROID: iommu/dma: Add support for DMA_ATTR_SYS_CACHE_ONLY_NWA

IOMMU_SYS_CACHE_ONLY_NWA allows buffers for non-coherent devices
to be mapped with the correct memory attributes so that the buffers
can be cached in the system cache, with a no write allocate cache policy.
However, this property is only usable by drivers that invoke the
IOMMU API directly; it is not usable by drivers that use the DMA API.

Thus, introduce DMA_ATTR_SYS_CACHE_ONLY_NWA, so that drivers for
non-coherent devices that use the DMA API can use it to specify if
they want a buffer to be cached in the system cache.

Bug: 176778547
Change-Id: Ic812a1fb144a58deb4279c2bf121fc6cc4c3b208
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>