block: Decouple block device "commit all" from DriveInfo

do_commit() and mux_proc_byte() iterate over the list of drives
defined with drive_init().  This misses host block devices defined by
other means.  Such means don't exist now, but will be introduced later
in this series.

Change them to use new bdrv_commit_all(), which iterates over all host
block devices.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/blockdev.c b/blockdev.c
index b5570f4..d74cd1d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -486,16 +486,16 @@
 
 void do_commit(Monitor *mon, const QDict *qdict)
 {
-    int all_devices;
-    DriveInfo *dinfo;
     const char *device = qdict_get_str(qdict, "device");
+    BlockDriverState *bs;
 
-    all_devices = !strcmp(device, "all");
-    QTAILQ_FOREACH(dinfo, &drives, next) {
-        if (!all_devices)
-            if (strcmp(bdrv_get_device_name(dinfo->bdrv), device))
-                continue;
-        bdrv_commit(dinfo->bdrv);
+    if (!strcmp(device, "all")) {
+        bdrv_commit_all();
+    } else {
+        bs = bdrv_find(device);
+        if (bs) {
+            bdrv_commit(bs);
+        }
     }
 }