perf bpf: Fixup include and examples install messages

perf bpf: Fixup include and examples install messages

Before:

  INSTALL  lib
install include/bpf/*.h '/home/acme/lib/include/perf/bpf'
  INSTALL  lib
install examples/bpf/*.c '/home/acme/lib/examples/perf/bpf'

After:

  INSTALL  lib
  INSTALL  include/bpf
  INSTALL  lib
  INSTALL  examples/bpf

Reported-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: dd8e4ead6e98 ("perf bpf: Add bpf.h to be used in eBPF proggies")
Fixes: 8f12a2ff00e5 ("perf bpf: Add 'examples' directories")
Link: https://lkml.kernel.org/n/tip-icljqe87e8pak8mu6mkki9d4@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>