Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 01a1101..a7b3421 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -129,7 +129,7 @@
 	if (!cancel_delayed_work(&linkwatch_work))
 		return;
 
-	/* Otherwise we reschedule it again for immediate exection. */
+	/* Otherwise we reschedule it again for immediate execution. */
 	schedule_delayed_work(&linkwatch_work, 0);
 }