devlink: introduce devlink_nl_put_u64()

Add devlink_nl_put_u64() that abstracts padding for u64 values.
All u64 values are passed with the very same padding option.

Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://patch.msgid.link/20241023131248.27192-2-przemyslaw.kitszel@intel.com


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