lib: move freader into buildid.h

Move struct freader and prototypes of the functions operating on it into
the buildid.h.

This allows reusing freader outside buildid, e.g. for file dynptr
support added later.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/20251026203853.135105-4-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
3 files changed