wifi: brcmfmac: support AP isolation to restrict reachability between stations

wifi: brcmfmac: support AP isolation to restrict reachability between stations

hostapd & wpa_supplicant userspace daemons exposes an AP mode specific
config file parameter "ap_isolate" to the user, which is used to control
low-level bridging of frames between the stations associated in the BSS.

In driver, handle this user setting in the newly defined cfg80211_ops
function brcmf_cfg80211_change_bss() by enabling "ap_isolate" IOVAR in
the firmware.

In AP mode, the "ap_isolate" value from the cfg80211 layer represents,
 0 = allow low-level bridging of frames between associated stations
 1 = restrict low-level bridging of frames to isolate associated stations
-1 = do not change existing setting

Signed-off-by: Wright Feng <wright.feng@cypress.com>
Signed-off-by: Chi-hsien Lin <chi-hsien.lin@cypress.com>
Signed-off-by: Gokul Sivakumar <gokulkumar.sivakumar@infineon.com>
[arend: indicate ap_isolate support in struct wiphy::bss_param_support]
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Link: https://patch.msgid.link/20250817190435.1495094-5-arend.vanspriel@broadcom.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>