CONFIG_IKCONFIG_PROC is required by BPF selftests, otherwise we get
errors like this:

 libbpf: failed to open system Kconfig
 libbpf: failed to load object 'kprobe_multi'
 libbpf: failed to load BPF skeleton 'kprobe_multi': -22

It's because /proc/config.gz is opened in bpf_object__read_kconfig_file()
in tools/lib/bpf/libbpf.c:

        file = gzopen("/proc/config.gz", "r");

So this patch enables CONFIG_IKCONFIG and CONFIG_IKCONFIG_PROC in
tools/testing/selftests/bpf/config.

Suggested-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 tools/testing/selftests/bpf/config | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index 763db63a3890..8d7faff33c54 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -53,3 +53,5 @@ CONFIG_NF_DEFRAG_IPV4=y
 CONFIG_NF_DEFRAG_IPV6=y
 CONFIG_NF_CONNTRACK=y
 CONFIG_USERFAULTFD=y
+CONFIG_IKCONFIG=y
+CONFIG_IKCONFIG_PROC=y
-- 
2.34.1