add a "ksym" iterator which provides access to a "struct kallsym_iter"
for each symbol. Intent is to support more flexible symbol parsing
as discussed in [1].
[1] https://lore.kernel.org/all/YjRPZj6Z8vuLeEZo@krava/
Suggested-by: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>