[nrf noup] boot: zephyr: Kconfig RSA phaseout

changing defaults

Signed-off-by: Mateusz Michalek <mateusz.michalek@nordicsemi.no>

Author: michalek-no

boot/zephyr/Kconfig

@@ -251,7 +251,7 @@ config BOOT_SIGNATURE_TYPE_PURE_ALLOW
 choice BOOT_SIGNATURE_TYPE
 	prompt "Signature type"
 	default BOOT_SIGNATURE_TYPE_ED25519 if SOC_NRF54L15_CPUAPP || SOC_NRF54H20_CPUAPP
-	default BOOT_SIGNATURE_TYPE_RSA
+	default BOOT_SIGNATURE_TYPE_ECDSA_P256
 
 config BOOT_SIGNATURE_TYPE_NONE
 	bool "No signature; use only hash check"