selftests/bpf: Do not export subtest as standalone test

selftests/bpf: Do not export subtest as standalone test

Two subtests in ksyms_module.c are not qualified as static, so these
subtests are exported as standalone tests in tests.h and lead to
confusion for the output of "./test_progs -t ksyms_module".

By using the following command ...

  grep "^void \(serial_\)\?test_[a-zA-Z0-9_]\+(\(void\)\?)" \
      tools/testing/selftests/bpf/prog_tests/*.c | \
	awk -F : '{print $1}' | sort | uniq -c | awk '$1 != 1'

... one finds out that other tests also have a similar problem, so
fix these tests by marking subtests in these tests as static.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220208065444.648778-1-houtao1@huawei.com