measure/inject operate on the monitor interface only (WiFiCsiController and
PacketInjector use FeitCSImon), and measureCsi()/injectPackets() bring the AP
interface down anyway; only ftm() uses it. Creating the AP unconditionally in
initInterface() makes setApMode()/bring-up fail on no-IR channels (e.g. 5/6 GHz
under the world regdomain 00), and the resulting netlink error propagates as an
uncaught exception that aborts the whole run with
"command failed: No such device (-19)".
Create the AP interface only when an FTM mode is requested, and guard the
now-optional AP teardown in the measure/inject paths.
