ARM: dts: hisilicon: fix errors detected by root-node.yaml

Make the memory node name match the regex "^memory(@[0-9a-f]+)?$" which
is described in memory.yaml. Otherwise, it will be treated as root node,
and misreported by root-node.yaml.

Errors misreported by root-node.yaml:
/: memory: False schema does not allow {'device_type': ['memory'], 'reg':

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>