block: block_int: include qerror.h

Several block/ files are relying on qerror.h being provided by
qapi-types.h. Fix this, as a future commit will change qapi-types.h
not to provide qerror.h.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>

block_int.h

@@ -30,6 +30,7 @@
 #include "qemu-coroutine.h"
 #include "qemu-timer.h"
 #include "qapi-types.h"
+#include "qerror.h"
 
 #define BLOCK_FLAG_ENCRYPT          1
 #define BLOCK_FLAG_COMPAT6          4