Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 239083b..b759896 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -474,7 +474,7 @@
 extern void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst);
 
 /**
- * skb_dst_is_noref - Test if skb dst isnt refcounted
+ * skb_dst_is_noref - Test if skb dst isn't refcounted
  * @skb: buffer
  */
 static inline bool skb_dst_is_noref(const struct sk_buff *skb)