basecmd: Change "move queue empty" error to "move queue overflow"

Use a more clear error message.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/basecmd.c

@@ -91,7 +91,7 @@ move_alloc(void)
     irqstatus_t flag = irq_save();
     struct move_freed *mf = move_free_list;
     if (!mf)
-        shutdown("Move queue empty");
+        shutdown("Move queue overflow");
     move_free_list = mf->next;
     irq_restore(flag);
     return mf;