tests: Fix ap-mgmt-fuzzer build configuration to match libap.a

tests: Fix ap-mgmt-fuzzer build configuration to match libap.a

Missing CONFIG_AIRTIME_POLICY=y made the offset of struct
hostapd_iface::prev_wmm different between libap.a and ap-mgmt-fuzzer.o
which resulted in odd fuzzing failures due to a memcpy to
ctx.iface->prev_wmm ending up writing on top of the ctx.hapd and in
particular, on top of ctx.hapd.iface pointer.

Credit to OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15013
Credit to OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15014
Credit to OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15015
Credit to OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15017
Credit to OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15019
Credit to OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15020
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>