block/raw: Fix to forward method bdrv_media_changed()

Block driver "raw" forwards most methods to the underlying block
driver.  However, it doesn't implement method bdrv_media_changed().
Makes bdrv_media_changed() always return -ENOTSUP.

I believe -fda /dev/fd0 gives you raw over host_floppy, and disk
change detection (fdc register 7 bit 7) is broken.  Testing my theory
requires a computer museum, though.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/raw.c

diff --git a/block/raw.c b/block/raw.c
index 555db4f..f197479 100644
--- a/block/raw.c
+++ b/block/raw.c
@@ -75,6 +75,11 @@
     return bdrv_is_inserted(bs->file);
 }
 
+static int raw_media_changed(BlockDriverState *bs)
+{
+    return bdrv_media_changed(bs->file);
+}
+
 static void raw_eject(BlockDriverState *bs, int eject_flag)
 {
     bdrv_eject(bs->file, eject_flag);
@@ -137,8 +142,10 @@
     .bdrv_discard       = raw_discard,
 
     .bdrv_is_inserted   = raw_is_inserted,
+    .bdrv_media_changed = raw_media_changed,
     .bdrv_eject         = raw_eject,
     .bdrv_set_locked    = raw_set_locked,
+
     .bdrv_ioctl         = raw_ioctl,
     .bdrv_aio_ioctl     = raw_aio_ioctl,