[nrf noup] entropy: Add fake entropy nRF PRNG driver

This adds temporary entropy driver simulation for
nRF54l09 device since final entropy source is not
available yet.

TODO: Remove this commit when proper solution will
be available.

Signed-off-by: Rafał Kuźnia <[email protected]>
(cherry picked from commit 4e83e09)

Author: e-rk

dts/arm/nordic/nrf54l09_enga_cpuapp.dtsi

@@ -18,6 +18,7 @@ nvic: &cpuapp_nvic {};
 / {
 	chosen {
 		zephyr,bt-hci = &bt_hci_controller;
+		zephyr,entropy = &prng;
 	};
 
 	soc {
@@ -30,6 +31,11 @@ nvic: &cpuapp_nvic {};
 		compatible = "zephyr,psa-crypto-rng";
 		status = "disabled";
 	};
+
+	prng: prng {
+		compatible = "nordic,entropy-prng";
+		status = "okay";
+	};
 };
 
 &bt_hci_controller {