hostapd: Work around lack of MLME support

hostapd: Work around lack of MLME support

hostap MLME uses Linux data structures and definitions not available
in FreeBSD. The ability for hostapd to select the frequency (channel)
depends Linux MLME, though strictly it's not required. Work around the
Linux MLME requirement to configure device frequency.

The detailed description is: hostapd will only set the channel (frequency)
when Linux MLME is configured. Enabling NEED_AP_MLME will result in
numerous build errors due do Linux data structures and definitions not
available under FreeBSD. The code to set the frequency from the selected
channel is only within the NEED_AP_MLME code path because without MLME,
hostapd_get_hw_features() is an inline that always returns -1 whereas with
MLME hostapd_get_hw_features() will obtain hardware features from the
kernel. Until such time we simply set the frequency as configured.

PR:		276375
MFC after:	1 month