arm64: dts: hikey: 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.

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