Merge branch 'bpf/selftests: page size fixes'

Yauheni Kaliuta says:

====================

A set of fixes for selftests to make them working on systems with PAGE_SIZE > 4K
+ cleanup (version) and ringbuf_multi extention.
---
v3->v4:
- zero initialize BPF programs' static variables;
- add bpf_map__inner_map to libbpf.map in alphabetical order;
- add bpf_map__set_inner_map_fd test to ringbuf_multi;

v2->v3:
 - reorder: move version removing patch first to keep main patches in
   one group;
 - rename "selftests/bpf: pass page size from userspace in sockopt_sk"
   as suggested;
 - convert sockopt_sk test to use ASSERT macros;
 - set page size from userspace
 - split patches to pairs userspace/bpf. It's easier to check that
   every conversion works as expected;

v1->v2:

- add missed 'selftests/bpf: test_progs/sockopt_sk: Convert to use BPF skeleton'
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>