ath6kl: allow deepsleep_suspend function when wlan interface down

Aafter wlan interface is down WLAN_ENABLED flags will be cleared and
deepsleep_suspend function will be blocked in this senario. This patch
allows deepsleep_suspend function when wlan interface down by removed
the WLAN_ENABLED flag checking.

kvalo: fix commit log

Signed-off-by: Ming Jiang <mjiang@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>