BACKPORT: FROMLIST: KVM: arm64: iommu: Add hypercall for map_sg

Add a new type struct kvm_iommu_sg, that describes a simple sglist,
and a hypercall that can consume it while calling the map_pages ops.

Link: https://lore.kernel.org/all/20241212180423.1578358-57-smostafa@google.com/



Bug: 357781595
Bug: 384432312

Change-Id: I16d7ab89fa84baf356f4f50980a839c08e526f0f
Signed-off-by: Mostafa Saleh <smostafa@google.com>