arm64: Switch to non coherent DMA operations

By default, arm64 assumes that all devices are coherent. This is
a poor assumption. Switch to using the noncoherent DMA APIs to
allow for proper cache operations.

Change-Id: I0cbbda20eed561e7a1d275c3fcc7db229c6a3639
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>