Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/fs/mbcache.c b/fs/mbcache.c
index a25444ab..2f174be 100644
--- a/fs/mbcache.c
+++ b/fs/mbcache.c
@@ -542,7 +542,7 @@
  * mb_cache_entry_find_first()
  *
  * Find the first cache entry on a given device with a certain key in
- * an additional index. Additonal matches can be found with
+ * an additional index. Additional matches can be found with
  * mb_cache_entry_find_next(). Returns NULL if no match was found. The
  * returned cache entry is locked for shared access ("multiple readers").
  *