arm64: dts: hikey960: Remove keep-power-in-suspend property

Remove the keep-power-in-suspend property because it keeps wifi power
on during suspend. This property is only required when enabling WoWLAN
and should only be enabled based on need. Also remove dupplicate property

Signed-off-by: Ryan Grachek <ryan@edited.us>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>