blkif: kill some repetitions in protocol description

The whole block describing multiqueue support was repeated
two times.

There also was some repetition in the description of the
'discard-enable' property.

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Konrad Rzeszutek Will <Konrad.wilk@oracle.com>

xen/include/public/io/blkif.h

@@ -216,10 +216,9 @@
  *      Default Value:  1
  *
  *      This optional property, set by the toolstack, instructs the backend
- *      to offer discard to the frontend. If the property is missing the
- *      backend should offer discard if the backing storage actually supports
- *      it. This optional property, set by the toolstack, requests that the
- *      backend offer, or not offer, discard to the frontend.
+ *      to offer (or not to offer) discard to the frontend. If the property
+ *      is missing the backend should offer discard if the backing storage
+ *      actually supports it.
  *
  * discard-alignment
  *      Values:         <uint32_t>
@@ -450,54 +449,6 @@
  *
  */
 
-/*
- * Multiple hardware queues/rings:
- * If supported, the backend will write the key "multi-queue-max-queues" to
- * the directory for that vbd, and set its value to the maximum supported
- * number of queues.
- * Frontends that are aware of this feature and wish to use it can write the
- * key "multi-queue-num-queues" with the number they wish to use, which must be
- * greater than zero, and no more than the value reported by the backend in
- * "multi-queue-max-queues".
- *
- * For frontends requesting just one queue, the usual event-channel and
- * ring-ref keys are written as before, simplifying the backend processing
- * to avoid distinguishing between a frontend that doesn't understand the
- * multi-queue feature, and one that does, but requested only one queue.
- *
- * Frontends requesting two or more queues must not write the toplevel
- * event-channel and ring-ref keys, instead writing those keys under sub-keys
- * having the name "queue-N" where N is the integer ID of the queue/ring for
- * which those keys belong. Queues are indexed from zero.
- * For example, a frontend with two queues must write the following set of
- * queue-related keys:
- *
- * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
- * /local/domain/1/device/vbd/0/queue-0 = ""
- * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>"
- * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>"
- * /local/domain/1/device/vbd/0/queue-1 = ""
- * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>"
- * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"
- *
- * It is also possible to use multiple queues/rings together with
- * feature multi-page ring buffer.
- * For example, a frontend requests two queues/rings and the size of each ring
- * buffer is two pages must write the following set of related keys:
- *
- * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
- * /local/domain/1/device/vbd/0/ring-page-order = "1"
- * /local/domain/1/device/vbd/0/queue-0 = ""
- * /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>"
- * /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>"
- * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>"
- * /local/domain/1/device/vbd/0/queue-1 = ""
- * /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>"
- * /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>"
- * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"
- *
- */
-
 /*
  * STATE DIAGRAMS
  *