ynl: netdev: drop unnecessary enum-as-flags

enum-as-flags can be used when enum declares bit positions but
we want to carry bitmask in an attribute. If the definition
is already provided as flags there's no need to indicate
the flag-iness of the attribute.

Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20231003153416.2479808-2-kuba@kernel.org


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