blockjob: Implement block_job_set_speed() centrally

All block job drivers support .set_speed and all of them duplicate the
same code to implement it. Move that code to blockjob.c and remove the
now useless callback.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>

include/block/blockjob.h

@@ -29,6 +29,8 @@
 #include "block/block.h"
 #include "qemu/ratelimit.h"
 
+#define BLOCK_JOB_SLICE_TIME 100000000ULL /* ns */
+
 typedef struct BlockJobDriver BlockJobDriver;
 typedef struct BlockJobTxn BlockJobTxn;
 

include/block/blockjob_int.h

@@ -41,9 +41,6 @@ struct BlockJobDriver {
     /** String describing the operation, part of query-block-jobs QMP API */
     BlockJobType job_type;
 
-    /** Optional callback for job types that support setting a speed limit */
-    void (*set_speed)(BlockJob *job, int64_t speed, Error **errp);
-
     /** Mandatory: Entrypoint for the Coroutine. */
     CoroutineEntry *start;