To provide VM with the ability to get device IO memory with NormalNC
property, map device MMIO in KVM for ARM64 at stage2 as NormalNC.
Having NormalNC S2 default puts guests in control (based on [1],
"Combining stage 1 and stage 2 memory type attributes") of device
MMIO regions memory mappings. The rules are summarized below:
([(S1) - stage1], [(S2) - stage 2])

S1           |  S2           | Result
NORMAL-WB    |  NORMAL-NC    | NORMAL-NC
NORMAL-WT    |  NORMAL-NC    | NORMAL-NC
NORMAL-NC    |  NORMAL-NC    | NORMAL-NC
DEVICE<attr> |  NORMAL-NC    | DEVICE<attr>

Still this cannot be generalized to non PCI devices such as GICv2.
There is insufficient information and uncertainity in the behavior
of non PCI driver. A driver must indicate support using the
new flag VM_ALLOW_ANY_UNCACHED.

Adapt KVM to make use of the flag VM_ALLOW_ANY_UNCACHED as indicator to
activate the S2 setting to NormalNc.

[1] section D8.5.5 of DDI0487J_a_a-profile_architecture_reference_manual.pdf
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Ankit Agrawal <ankita@nvidia.com>
Link: https://lore.kernel.org/r/20240224150546.368-4-ankita@nvidia.comSigned-off-by: Oliver Upton <oliver.upton@linux.dev>