Update devlink documentation to match current code:
- describe health reporter defaults (it's currently under "callbacks"),
best-effort auto-dump, and port-scoped reporters
- fix generic parameter names and values
- fix nested devlink setup wording and registration ordering
Link: https://patch.msgid.link/20260613165846.2913092-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>