selftests/bpf: ensure all CI arches set CONFIG_BPF_KPROBE_OVERRIDE=y

Turns out CONFIG_BPF_KPROBE_OVERRIDE=y is only enabled in x86-64 CI, but
is not set on aarch64, causing CI failures ([0]).

Move CONFIG_BPF_KPROBE_OVERRIDE=y to arch-agnostic CI config.

  [0] https://github.com/kernel-patches/bpf/actions/runs/6122324047/job/16618390535



Fixes: 7182e564 ("selftests/bpf: Add kprobe_multi override test")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230912055928.1704269-1-andrii@kernel.org


Signed-off-by: Alexei Starovoitov <ast@kernel.org>