ath5k: Storage class should be before const qualifier

commit 8e218fb2 reverted the previous
patch (commit 925be8a3).

The C99 specification states in section 6.11.5:

The placement of a storage-class specifier other than at the
beginning of the declaration specifiers in a declaration is an
obsolescent feature.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>