ANDROID: iommu/arm-smmu: Expose s2cr and smr structs to impl

Move the arm_smmu_s2cr and arm_smmu_smr structs to the internal header
file, in order to expose them to the platform specific arm-smmu
implementations.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Bug: 146449535
Link: https://lore.kernel.org/linux-arm-msm/20191226221709.3844244-3-bjorn.andersson@linaro.org/
Change-Id: Ibd7decec866cf58a269730ccfcaae807dd849a10