configs: default activate CONFIG_RNG_STM32 for STM32MP13x platforms

Default embed this configuration. If OP-TEE PTA RNG is exposed, it means
that the RNG is managed by the secure world. Therefore, the RNG node
should be disabled in the device tree as an access would be denied
by the hardware firewall.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/configs/stm32mp13_defconfig b/configs/stm32mp13_defconfig
index 4e83753..ad23692 100644
--- a/configs/stm32mp13_defconfig
+++ b/configs/stm32mp13_defconfig
@@ -65,6 +65,7 @@
 CONFIG_DM_REGULATOR_SCMI=y
 CONFIG_RESET_SCMI=y
 CONFIG_DM_RNG=y
+CONFIG_RNG_STM32=y
 CONFIG_DM_RTC=y
 CONFIG_RTC_STM32=y
 CONFIG_SERIAL_RX_BUFFER=y