Fix "No such file or directory" without IOMMU
When IOMMU was disabled by default on BIOS configuration, it means that there is no device/iommu_group.
Thus rocm-qemu-setup raises "No such file or directory" error.
It might be helpful to check such a edge case and finally reports what is wrong.
Signed-off-by: Kentaro Hayashi kenhys@xdump.org