The entry-method property of the idle-states node should be "psci" as
described in the idle-states binding, since this is already the value of
enable-method in the CPU nodes. Fix it to get rid of a dtbs_check
warning.
Fixes: 9260918d3a4f ("arm64: dts: mt8192: Add cpu-idle-states")
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@xxxxxxxxxxxxx>