config: android-recommended: Disable BPF_UNPRIV_DEFAULT_OFF for netd

AOSP's `netd` process fails to start on Android S:

    E ClatdController: getClatEgress4MapFd() failure: Operation not permitted
    I netd    : Initializing ClatdController: 410us
    E netd    : Failed to start trafficcontroller: (Status[code: 1, msg: "Pinned map not accessible or does not exist: (/sys/fs/bpf/map_netd_cookie_tag_map): Operation not permitted"])
    E netd    : CRITICAL: sleeping 60 seconds, netd exiting with failure, crash loop likely!

And on Android R:

    I ClatdController: 4.9+ kernel and device shipped with P - clat ebpf might work.
    E ClatdController: getClatEgressMapFd() failure: Operation not permitted
    I netd    : Initializing ClatdController: 1409us
    E netd    : Failed to start trafficcontroller: (Status[code: 1, msg: "Pinned map not accessible or does not exist: (/sys/fs/bpf/map_netd_cookie_tag_map): Operation not permitted"])

These permission issues are caused by 08389d8 ("bpf: Add kconfig
knob for disabling unpriv bpf by default") because AOSP does not provide
netd the `SYS_ADMIN` capability, and also has no userspace support for
the `BPF` capability yet.

Cc: Amit Pundir <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Suggested-by: John Stultz <[email protected]>
[John suggested this in https://linaro.atlassian.net/browse/ACK-107?focusedCommentId=117382]
Signed-off-by: Marijn Suijten <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

kernel/configs/android-recommended.config

@@ -1,4 +1,5 @@
 #  KEEP ALPHABETICALLY SORTED
+# CONFIG_BPF_UNPRIV_DEFAULT_OFF is not set
 # CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS is not set
 # CONFIG_INPUT_MOUSE is not set
 # CONFIG_LEGACY_PTYS is not set