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/isdn/hdlc.h b/include/linux/isdn/hdlc.h
index 4b3ecc4..9652137 100644
--- a/include/linux/isdn/hdlc.h
+++ b/include/linux/isdn/hdlc.h
@@ -2,7 +2,7 @@
  * hdlc.h  --  General purpose ISDN HDLC decoder.
  *
  * Implementation of a HDLC decoder/encoder in software.
- * Neccessary because some ISDN devices don't have HDLC
+ * Necessary because some ISDN devices don't have HDLC
  * controllers.
  *
  * Copyright (C)