block: Fix compiler warning (-Werror=uninitialized)

The patch fixes a warning from gcc (Debian 4.6.3-14+rpi1) 4.6.3:

block/stream.c:141:22: error:
‘copy’ may be used uninitialized in this function [-Werror=uninitialized]

This is not a real bug - a better compiler would not complain.

Now 'copy' has always a defined value, so the check for ret >= 0
can be removed.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/stream.c

@@ -119,11 +119,12 @@ static void coroutine_fn stream_run(void *opaque)
             break;
         }
 
+        copy = false;
+
         ret = bdrv_is_allocated(bs, sector_num,
                                 STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
         if (ret == 1) {
             /* Allocated in the top, no need to copy.  */
-            copy = false;
         } else if (ret >= 0) {
             /* Copy if allocated in the intermediate images.  Limit to the
              * known-unallocated area [sector_num, sector_num+n).  */
@@ -138,7 +139,7 @@ static void coroutine_fn stream_run(void *opaque)
             copy = (ret == 1);
         }
         trace_stream_one_iteration(s, sector_num, n, ret);
-        if (ret >= 0 && copy) {
+        if (copy) {
             if (s->common.speed) {
                 delay_ns = ratelimit_calculate_delay(&s->limit, n);
                 if (delay_ns > 0) {