arm64: dts: qcom: x1-el2: Disable IRIS for now

arm64: dts: qcom: x1-el2: Disable IRIS for now

The reset and IOMMU management for remoteprocs like IRIS is implemented in
the hypervisor for older targets such as X1E [1]. When booting Linux/KVM
directly in EL2, this functionality is missing and the PAS interface
normally used by IRIS to boot the video firmware is not working.

The Venus driver supports starting the video firmware without using the PAS
interface. The same code also works for X1E when using KVM. However, for
the new IRIS dt-bindings it was decided to avoid using the dummy
"video-firmware" node in the device tree to describe the IOMMU [2].
Discussion is still ongoing how to describe this properly [3].

To avoid regressions when running using KVM, add a TODO in x1-el2.dtso for
now and disable IRIS even when it was enabled by the board.

[1]: https://resources.linaro.org/en/resource/sF8jXifdb9V1mUefdbfafa
[2]: https://lore.kernel.org/r/20250823155349.22344-2-krzysztof.kozlowski@linaro.org/
[3]: https://lore.kernel.org/r/20250819165447.4149674-12-mukesh.ojha@oss.qualcomm.com/

Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Link: https://lore.kernel.org/r/20250915-x1e-iris-dt-v2-3-1f928de08fd4@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>