Merge branch 'fix-lpm-map'

Yonghong Song says:

====================
A kernel page fault which happens in lpm map trie_get_next_key is reported
by syzbot and Eric. The issue was introduced by commit b471f2f1de8b
("bpf: implement MAP_GET_NEXT_KEY command for LPM_TRIE map").
Patch #1 fixed the issue in the kernel and patch #2 adds a multithreaded
test case in tools/testing/selftests/bpf/test_lpm_map.
====================

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