ath9k: ath9k_op_ps_wakeup() can be static

drivers/net/wireless/ath/ath9k/init.c:91:6: sparse: symbol 'ath9k_op_ps_wakeup' was not declared. Should it be static?
drivers/net/wireless/ath/ath9k/init.c:96:6: sparse: symbol 'ath9k_op_ps_restore' was not declared. Should it be static?
drivers/net/wireless/ath/ath9k/init.c:101:19: sparse: symbol 'ath9k_ps_ops' was not declared. Should it be static?

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>