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/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index 7898ea1..8d2eef1 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -35,10 +35,10 @@
  * Each cache must be registered so that it can be cleaned regularly.
  * When the cache is unregistered, it is flushed completely.
  *
- * Entries have a ref count and a 'hashed' flag which counts the existance
+ * Entries have a ref count and a 'hashed' flag which counts the existence
  * in the hash table.
  * We only expire entries when refcount is zero.
- * Existance in the cache is counted  the refcount.
+ * Existence in the cache is counted  the refcount.
  */
 
 /* Every cache item has a common header that is used