perf tools: Update header documentation on BPF_PROG_INFO

perf tools: Update header documentation on BPF_PROG_INFO

Update the perf.data file format description on header section
HEADER_BPF_PROG_INFO.

The information is taken from process_bpf_prog_info() and
write_bpf_prog_info() from file util/header.c.

Reviewed-by: Jan Polensky <japo@linux.ibm.com>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>