specs/qcow2: fix bitmap granularity qemu-specific note

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20170628120530.31251-2-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

docs/interop/qcow2.txt

@@ -575,8 +575,7 @@ Structure of a bitmap directory entry:
              17:    granularity_bits
                     Granularity bits. Valid values: 0 - 63.
 
-                    Note: Qemu currently doesn't support granularity_bits
-                    greater than 31.
+                    Note: Qemu currently supports only values 9 - 31.
 
                     Granularity is calculated as
                         granularity = 1 << granularity_bits