iommu/exynos: add support for reserved regions

The bootloader configures a reserved memory region for framebuffer,
which is protected by the IOMMU. The kernel-side driver is oblivious as
of which memory region is set up by the bootloader. In such case, the
IOMMU tries to reference the reserved region - which is not reserved in
the kernel anymore - and it results in an unrecoverable page fault. More
information about it is provided in [1].

Add support for reserved regions using iommu_dma_get_resv_regions().
For OF supported boards, this requires defining the region in the
iommu-addresses property of the IOMMU owner's node.

Link: https://lore.kernel.org/r/544ad69cba52a9b87447e3ac1c7fa8c3@disroot.org

 [1]
Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Link: https://lore.kernel.org/r/20250712-exynos-sysmmu-resv-regions-v1-1-e79681fcab1a@disroot.org


Signed-off-by: Will Deacon <will@kernel.org>