chore: cargo fmt

Author: Ivans-11

user/src/bin/fork_exit.rs

@@ -3,7 +3,7 @@
 
 #[macro_use]
 extern crate user_lib;
-use user_lib::{exit, fork, wait, waitpid, sched_yield};
+use user_lib::{exit, fork, sched_yield, wait, waitpid};
 
 const MAGIC: i32 = -0x10384;
 
@@ -27,4 +27,4 @@ extern "C" fn main() -> i32 {
     println!("waitpid {} ok.", pid);
     println!("exit pass.");
     0
-}
+}

user/src/bin/forktest_simple.rs

@@ -25,4 +25,4 @@ pub extern "C" fn main() -> i32 {
         println!("child process pid = {}, exit code = {}", pid, exit_code);
         0
     }
-}
+}

user/src/bin/phil_din_mutex.rs

@@ -106,4 +106,4 @@ pub extern "C" fn main() -> i32 {
     }
     println!("philosopher dining problem with mutex test passed!");
     0
-}
+}