drivers: rng: optee_rng: register to CONFIG_OPTEE_SERVICE_DISCOVERY

Changes optee_rng driver to register itself has a OP-TEE service so
that a device is bound for the driver when OP-TEE enumerates the
PTA RNG service.

Cc: Sughosh Ganu <sughosh.ganu@linaro.org>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
index 1614368..5dcf681 100644
--- a/drivers/rng/Kconfig
+++ b/drivers/rng/Kconfig
@@ -41,6 +41,7 @@
 config RNG_OPTEE
 	bool "OP-TEE based Random Number Generator support"
 	depends on DM_RNG && OPTEE
+	default y if OPTEE_SERVICE_DISCOVERY
 	help
 	  This driver provides support for the OP-TEE based Random Number
 	  Generator on ARM SoCs where hardware entropy sources are not
diff --git a/drivers/rng/optee_rng.c b/drivers/rng/optee_rng.c
index aa8ce86..410dfc0 100644
--- a/drivers/rng/optee_rng.c
+++ b/drivers/rng/optee_rng.c
@@ -11,6 +11,9 @@
 #include <dm/device.h>
 #include <dm/device_compat.h>
 #include <linux/sizes.h>
+#include <tee/optee_service.h>
+
+#define DRIVER_NAME	"optee-rng"
 
 #define TEE_ERROR_HEALTH_TEST_FAIL	0x00000001
 
@@ -35,6 +38,8 @@
 #define TA_HWRNG_UUID { 0xab7a617c, 0xb8e7, 0x4d8f, \
 			{ 0x83, 0x01, 0xd0, 0x9b, 0x61, 0x03, 0x6b, 0x64 } }
 
+OPTEE_SERVICE_DRIVER(optee_rng, TA_HWRNG_UUID, DRIVER_NAME);
+
 /** open_session_ta_hwrng() - Open session with hwrng Trusted App
  *
  * @dev:		device
@@ -177,7 +182,7 @@
 };
 
 U_BOOT_DRIVER(optee_rng) = {
-	.name = "optee-rng",
+	.name = DRIVER_NAME,
 	.id = UCLASS_RNG,
 	.ops = &optee_rng_ops,
 	.probe = optee_rng_probe,