ath5k: remove stale function declarations, make some functions static

Remove all unnecessary function declarations from ath5k.h.  Comment out
unused functions.  Remove ath5k_hw_get_tsf32(), which is too trivial to
be commented out.  Make functions static if suggested by sparse.  Make
ath5k_pm_ops static.

Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>