fix: 修复do_wait函数在wait所有子进程时,忘了释放锁就sleep的bug (#1089)

Signed-off-by: longjin <longjin@DragonOS.org>

kernel/src/process/exit.rs

@@ -175,6 +175,7 @@ fn do_wait(kwo: &mut KernelWaitOption) -> Result<usize, SystemError> {
                         break 'outer;
                     }
                 }
+                drop(rd_childen);
                 nanosleep(Duration::from_millis(100).into())?;
             }
         } else {