KVM: arm64: vgic-debug: Convert to use DEFINE_SEQ_ATTRIBUTE macro

Use DEFINE_SEQ_ATTRIBUTE macro to simplify the code.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200916025023.3992679-1-liushixin2@huawei.com