ARM: hisi: consolidate the hisilicon machine entries

The original patch was to add compatible string for Hi3519 soc
and do some cleanup.

Since the generic machine entry could meet most of the cases,
so I did a further cleanup to reuse it and just keep one machine
entry that needs map_io here.

Signed-off-by: Jiancheng Xue <xuejiancheng@huawei.com>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>