devlink: rename devlink_nl_instance_iter_dump() to "dumpit"

To have the name of the function consistent with the struct cb name,
rename devlink_nl_instance_iter_dump() to
devlink_nl_instance_iter_dumpit().

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>