Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>

kernel/mutex.c

diff --git a/kernel/mutex.c b/kernel/mutex.c
index a5889fb..c4195fa 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -245,7 +245,7 @@
 		}
 		__set_task_state(task, state);
 
-		/* didnt get the lock, go to sleep: */
+		/* didn't get the lock, go to sleep: */
 		spin_unlock_mutex(&lock->wait_lock, flags);
 		preempt_enable_no_resched();
 		schedule();