virtio: Expose VIRTIO_F_IOMMU_PLATFORM in device features

If we detect the VIRTIO_F_IOMMU_PLATFORM transport feature for a device,
then expose it in the device features.

Signed-off-by: Will Deacon <willdeacon@google.com>
[ Paul: pick from the Android tree. Rebase to the upstream ]
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Link: https://android.googlesource.com/platform/external/u-boot/+/9693bd26bfcfe77d6a1295a561420e08c5daf019


Reviewed-by: Simon Glass <sjg@chromium.org>