arm: dma-mapping: Export arch_setup_dma_ops symbol

Some test modules need to call "arch_setup_dma_ops" to setup
the proper dma operations.

Change-Id: Icc884b53c85941f59f84bed108b536cc18b8be60
Signed-off-by: Venkatesh Yadav Abbarapu <vabbar@codeaurora.org>