Properly round-trip the "operation code" for client requests.
sys/dev/xen/blkback/blkback.c:
In xbb_dispatch_dev() when processing a flush request,
correctly set bio->bio_caller1 to the request list (not
bare request) for the operation, as is expected by the
completion handler xbb_bio_done().
In xbb_get_resources(), initialize "operation" in the
driver's internal request object from the client's "ring
request", so it is correct when used to populate the reply
when this operation completes.
Submitted by: Roger Pau Monné
Sponsored by: Citrix Systems R&D
Reviewed by: gibbs