The DTSM is a mask that specifies which I/O Address Translation designation
types are supported.  Today QEMU only supports DT=1.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Message-Id: <20211203142706.427279-5-mjrosato@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>