fdc: fix implied seek while there is no media in drive

The Windows uses 'READ' command at the start of an instalation
without checking the 'dir' register. We have to abort the transfer
with an abnormal termination if there is no media in the drive.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

hw/fdc.c

@@ -159,6 +159,10 @@ static int fd_seek(FDrive *drv, uint8_t head, uint8_t track, uint8_t sect,
         drv->sect = sect;
     }
 
+    if (drv->bs == NULL || !bdrv_is_inserted(drv->bs)) {
+        ret = 2;
+    }
+
     return ret;
 }