Revert "nl80211: Remove duplicated check in nl80211_setup_ap()"

Revert "nl80211: Remove duplicated check in nl80211_setup_ap()"

This reverts commit 647862eb60c324015ea31293cc052558b5185ca4.

The second check of device_ap_sme looks like duplicated, but it isn't
actually. The trick is nl80211_create_monitor_interface may change that
variable value and the second evaluation may give a different result.

This definitely isn't a very clear code, but that change caused a
regression for drivers that:
1) Don't report NL80211_ATTR_DEVICE_AP_SME
2) Don't support monitor mode
3) Don't support subscribing for PROBE_REQ and/or ACTION frames
like brcmfmac. With such drivers hostapd doesn't start anymore.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>