arm64: dts: qcom: x1e80100: Add PCIe IOMMU

x1e80100 has an SMMUv3 connected to PCIe which is normally controlled by
Gunyah and is thus transparent to the OS. However if we boot Linux in
EL2, without Gunyah, we need to manage this IOMMU ourselves. To make
that easier, and since the hardware actually exists, just not "usually"
managed by Linux, describe it in the dts as "reserved".

Signed-off-by: Nikita Travkin <nikita@trvn.ru>
Link: https://lore.kernel.org/r/20250503-sc-el2-overlays-v2-4-24e9b4572e15@trvn.ru


Signed-off-by: Bjorn Andersson <andersson@kernel.org>