ARM: dts: stm32: bump PSCI to version 1.0 on stm32mp15x

Declare PSCI v1.0 support instead of v0.1 as the former is supported
by the PSCI firmware stacks stm32mp15x relies on.

Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>