doc: netlink: Fix formatting of op flags in generated .rst

Generate op flags as an inline list instead of a stringified python
value.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://lore.kernel.org/r/20240528140652.9445-4-donald.hunter@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>