Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/net/pppoe.c b/drivers/net/pppoe.c
index 78c0e3c..693aaef 100644
--- a/drivers/net/pppoe.c
+++ b/drivers/net/pppoe.c
@@ -115,7 +115,7 @@
  * 2) Session stage (MAC and SID are known)
  *
  * Ethernet frames have a special tag for this but
- * we use simplier approach based on session id
+ * we use simpler approach based on session id
  */
 static inline bool stage_session(__be16 sid)
 {