On the Qualcomm SoC as implemented on the Lenovo x13s the BIOS already

On the Qualcomm SoC as implemented on the Lenovo x13s the BIOS already
configures and makes use of the SMMU.  We need to keep those mappings
alive as otherwise the machine will die and reboot.  Unfortunately we
cannot simply set those domains to bypass, as when we set a domain to
bypass it is actually set to fault.  Instead reserve a domain and set
it to disabled, which behaves the same as if we used a bypass mapping.

With feedback from kettenis@