Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 8eaba5f..de9aef8 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -224,7 +224,7 @@
  * writing to 'state'.  It first should read from 'wakeup_count' and store
  * the read value.  Then, after carrying out its own preparations for the system
  * transition to a sleep state, it should write the stored value to
- * 'wakeup_count'.  If that fails, at least one wakeup event has occured since
+ * 'wakeup_count'.  If that fails, at least one wakeup event has occurred since
  * 'wakeup_count' was read and 'state' should not be written to.  Otherwise, it
  * is allowed to write to 'state', but the transition will be aborted if there
  * are any wakeup events detected after 'wakeup_count' was written to.