PR #143720 adds a requirement to the ACC dialect that every acc.loop
must have a seq, independent, or auto attribute for the 'default'
device_type. The standard has rules for how this can be intuited:
orphan/parallel/parallel loop: independent
kernels/kernels loop: auto
serial/serial loop: seq, unless there is a gang/worker/vector, at which
point it should be 'auto'.
This patch implements all of this rule as a 'cleanup' step on the IR
generation for combined/loop operations. Note that the test impact is
much less since I inadvertently have my 'operation' terminating curley
matching the end curley from 'attribute' instead of the front of the
line, so I've added sufficient tests to ensure I captured the above.
574f77a1ee