Merge branch 'bpf-xdp-add-tracepoint-to-xdp-attaching-failure'

Leon Hwang says:

====================
bpf, xdp: Add tracepoint to xdp attaching failure

This series introduces a new tracepoint in bpf_xdp_link_attach(). By
this tracepoint, error message will be captured when error happens in
dev_xdp_attach(), e.g. invalid attaching flags.

v4 -> v5:
* Initialise the extack variable.
* Fix code style issue of variable declaration lines.

v3 -> v4:
* Fix selftest-crashed issue.
====================

Link: https://lore.kernel.org/r/20230801142621.7925-1-hffilwlqm@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>