Put storage class first and remove unreachable statement (#505)
Fixes following greenhills compiler warnings
* etl/include/etl/message_router.h", line 2434 (col. 11): warning #111-D: statement is unreachable
* etl/include/etl/char_traits.h", line 105 (col. 19): warning #82-D: storage class is not first
Co-authored-by: Jochen Steinmann <jochen.steinmann2@de.bosch.com>
