iommu/pages: Fix iommu_pages_flush_incoherent() for non-x86

The dma_sync_single_for_device() function expects a dma_addr_t, but
iommu_pages_flush_incoherent() was incorrectly passing a virtual
address.

Since iommu_pages_start_incoherent() enforces a 1:1 mapping between
DMA addresses and physical addresses (checked via WARN_ON), we can
convert the virtual address to a physical address before passing it to
the DMA API.

This also  matches the behaviour of the other non-x86 in
iommu_pages_free_incoherent(), which uses virt_to_phys(virt);

Fixes: 36ae67b13976 ("iommu/pages: Add support for incoherent IOMMU page table walkers")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>