ath9k: ar9002_initvals: Remove unused array 'ar9280PciePhy_clkreq_off_L1_9280'

Fixes the following W=1 kernel build warning(s):

 drivers/net/wireless/ath/ath9k/ar9002_initvals.h:900:18: warning: ‘ar9280PciePhy_clkreq_off_L1_9280’ defined but not used [-Wunused-const-variable=]

Cc: QCA ath9k Development <ath9k-devel@qca.qualcomm.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200826093401.1458456-18-lee.jones@linaro.org