dts: arm: stm32 entropy with nist configuration for the RNG

The nist-config and health-test-magic properties are added
to the dtsi file, in the RNG node for the stm32 devices
that supports the RNG entropy source validation.
The health-test-magic nb exists on stm32l552 stm32h723/7a3.

Signed-off-by: Francois Ramu <francois.ramu@st.com>