Merge branch 'non-jit-btf-func_info'

Yonghong Song says:

====================
Commit 838e9690 ("bpf: Introduce bpf_func_info")
added bpf func info support. The userspace is able
to get better ksym's for bpf programs with jit, and
is able to print out func prototypes.

For a program containing func-to-func calls, the existing
implementation returns user specified number of function
calls and BTF types if jit is enabled. If the jit is not
enabled, it only returns the type for the main function.

This is undesirable. Interpreter may still be used
and we should keep feature identical regardless of
whether jit is enabled or not.
This patch fixed this discrepancy.

The following example shows bpftool output for
the bpf program in selftests test_btf_haskv.o when jit
is disabled:
  $ bpftool prog dump xlated id 1490
  int _dummy_tracepoint(struct dummy_tracepoint_args * arg):
     0: (85) call pc+2#__bpf_prog_run_args32
     1: (b7) r0 = 0
     2: (95) exit
  int test_long_fname_1(struct dummy_tracepoint_args * arg):
     3: (85) call pc+1#__bpf_prog_run_args32
     4: (95) exit
  int test_long_fname_2(struct dummy_tracepoint_args * arg):
     5: (b7) r2 = 0
     6: (63) *(u32 *)(r10 -4) = r2
     7: (79) r1 = *(u64 *)(r1 +8)
     8: (15) if r1 == 0x0 goto pc+9
     9: (bf) r2 = r10
    10: (07) r2 += -4
    11: (18) r1 = map[id:1173]
    13: (85) call bpf_map_lookup_elem#77088
    14: (15) if r0 == 0x0 goto pc+3
    15: (61) r1 = *(u32 *)(r0 +4)
    16: (07) r1 += 1
    17: (63) *(u32 *)(r0 +4) = r1
    18: (95) exit
  $ bpftool prog dump jited id 1490
    no instructions returned
====================

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