Merge branch 'bpf-offload-report-dev'

Jakub Kicinski says:

====================
This series is a redo of reporting offload device information to
user space after the first attempt did not take into account name
spaces.  As requested by Kirill offloads are now protected by an
r/w sem.  This allows us to remove the workqueue and free the
offload state fully when device is removed (suggested by Alexei).

Net namespace is reported with a device/inode pair.

The accompanying bpftool support is placed in common code because
maps will have very similar info.  Note that the UAPI information
can't be nicely encapsulated into a struct, because in case we
need to grow the device information the new fields will have to
be added at the end of struct bpf_prog_info, we can't grow
structures in the middle of bpf_prog_info.

v3:
 - use dev_get_by_index();
 - redo ns code (new patch 6).
v2:
 - rework the locking in patch 1 (use RCU instead of locking
   dependencies);
 - grab RTNL for a short time in patch 6;
 - minor update to the test in patch 8.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>