Merge branch 'bpf: arena prerequisites'

Alexei Starovoitov says:

====================
These are bpf_arena prerequisite patches.
Useful on its own.

Alexei Starovoitov (5):
  bpf: Allow kfuncs return 'void *'
  bpf: Recognize '__map' suffix in kfunc arguments
  bpf: Plumb get_unmapped_area() callback into bpf_map_ops
  libbpf: Allow specifying 64-bit integers in map BTF.
  bpf: Tell bpf programs kernel's PAGE_SIZE
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>