arm64: Fix the DMA mmap and get_sgtable API with DMA_ATTR_FORCE_CONTIGUOUS

While honouring the DMA_ATTR_FORCE_CONTIGUOUS on arm64 (commit
44176bb3: "arm64: Add support for DMA_ATTR_FORCE_CONTIGUOUS to
IOMMU"), the existing uses of dma_mmap_attrs() and dma_get_sgtable()
have been broken by passing a physically contiguous vm_struct with an
invalid pages pointer through the common iommu API.

Since the coherent allocation with DMA_ATTR_FORCE_CONTIGUOUS uses CMA,
this patch simply reuses the existing swiotlb logic for mmap and
get_sgtable.

Note that the current implementation of get_sgtable (both swiotlb and
iommu) is broken if dma_declare_coherent_memory() is used since such
memory does not have a corresponding struct page. To be addressed in a
subsequent patch.

Fixes: 44176bb3

 ("arm64: Add support for DMA_ATTR_FORCE_CONTIGUOUS to IOMMU")
Reported-by: Andrzej Hajda <a.hajda@samsung.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>