ath9k: Fix wow.c compilation

The HW routines to set various WoW registers are present
in wow.c. For some reason, it has been compiled as part
of the main ath9k.ko module all this time, when it should
really be part of ath9k_hw.ko. This patch renames the file to
ar9003_wow.ko and adds it to ath9k_hw.ko.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>