arm64: dts: Fix various entry-method properties to reflect documentation

arm64: dts: Fix various entry-method properties to reflect documentation

The idle-states binding documentation[1] mentions that the
'entry-method' property is required on 64-bit platforms and must be
set to "psci".

Linux commit a13f18f59d26 ("Documentation: arm: Fix typo in the idle-states
bindings examples") attempted to fix this earlier but clearly more is
needed.

Linux docs:
Documentation/devicetree/bindings/arm/idle-states.txt (see
idle-states node)

Signed-off-by: Amit Kucheria <[email protected]>
Acked-by: Sudeep Holla <[email protected]>
Acked-by: Li Yang <[email protected]>
Signed-off-by: Olof Johansson <[email protected]>
Signed-off-by: Michal Simek <[email protected]>