ath10k: Revert "ath10k: add cleanup in ath10k_sta_state()"

This reverts commit 334f5b61.

This caused ath10k_snoc on Qualcomm MSM8998, SDM845 and QCS404 platforms to
trigger an assert in the firmware:

err_qdi.c:456:EF:wlan_process:1:cmnos_thread.c:3900:Asserted in wlan_vdev.c:_wlan_vdev_up:3219

Revert the offending commit for now.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>