A few documentation updates

src/kernel/synch.rs

@@ -43,12 +43,12 @@ impl Semaphore {
         machine.interrupt.set_status(old_status);
     }
 
-    ///      Increment semaphore value, waking up a waiting thread if any.
-    ///	As with P(), this operation must be atomic, so we need to disable
-    ///	interrupts.
+    /// Increment semaphore value, waking up a waiting thread if any.
+    /// As with P(), this operation must be atomic, so we need to disable
+    /// interrupts.
     ///
     /// scheduler::ready_to_run() assumes that interrupts
-    ///	are disabled when it is called.
+    /// are disabled when it is called.
     ///
     /// ### Parameters
     /// - **machine** the machine where the threads are executed