Do not use the generic bss_info_handler() design to fetch all scan
results into temporary memory buffer. Instead, use a separate BSS info
handler that fetches the requested information without fully parsing the
BSS entries and without allocating any memory for collecting all the
results.
This is also simplifying bss_info_handler() and nl80211_parse_bss_info()
design by getting rid of the special case that was used only for
nl80211_get_assoc_freq() and not normal scan result fetching.
Signed-off-by: Jouni Malinen <j@w1.fi>