Use DEFINE_SEQ_ATTRIBUTE macro to simplify the code.

Link: https://lore.kernel.org/r/20200916025025.3992783-1-liushixin2@huawei.comSigned-off-by: NLiu Shixin <liushixin2@huawei.com>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: NThierry Reding <treding@nvidia.com>