tools: libbpf: don't return '.text' as a program for multi-function programs

Make bpf_program__next() skip over '.text' section if object file
has pseudo calls.  The '.text' section is hardly a program in that
case, it's more of a storage for code of functions other than main.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>