msm: ipa: fix IOMMU symbols usage

Some IOMMU symbols used in msm-4.4 are no longer valid on
msm-4.8. Change IOMMU_DEVICE to IOMMU_MMIO and remove usage of
msm_iommu_get_bus().

CRS-Fixed: 1077422
Signed-off-by: Amir Levy <alevy@codeaurora.org>
Change-Id: I5ff82b7f2f94fdd75c3b3116977bc8144605bf7d