perf bpf: Synthesize bpf events with bpf_program__get_prog_info_linear()

With bpf_program__get_prog_info_linear, we can simplify the logic that
synthesizes bpf events.

This patch doesn't change the behavior of the code.

Commiter notes:

Needed this (for all four variables), suggested by Song, to overcome
build failure on debian experimental cross building to MIPS 32-bit:

  -               u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(info->prog_tags);
  +               u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(uintptr_t)(info->prog_tags);

  util/bpf-event.c: In function 'perf_event__synthesize_one_bpf_prog':
  util/bpf-event.c:143:35: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
     u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(info->prog_tags);
                                     ^
  util/bpf-event.c:144:22: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
     __u32 *prog_lens = (__u32 *)(info->jited_func_lens);
                        ^
  util/bpf-event.c:145:23: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
     __u64 *prog_addrs = (__u64 *)(info->jited_ksyms);
                         ^
  util/bpf-event.c:146:22: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
     void *func_infos = (void *)(info->func_info);
                        ^
  cc1: all warnings being treated as errors

Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: kernel-team@fb.com
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislav Fomichev <sdf@google.com>
Link: http://lkml.kernel.org/r/20190312053051.2690567-5-songliubraving@fb.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>