ath6kl: Check sme state before delivering disconnect event to cfg80211

 In some random cases, the firmware is sending two disconnect event to
 the host. In the current model, both diconnect events are passed to
 cfg80211 without checking local sme state machine, which is screwing
 cfg80211 layer state.

Signed-off-by: Raja Mani <rmani@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>