tee: change return code for REE FS supplicant cmd

If OP-TEE core is compiled with support of REE FS and RPMB
at the same time (CFG_RPMB_FS ?= y; CFG_RPMB_FS ?= y), and persistent
storage API is used with TEE_STORAGE_PRIVATE storage id, it will
lead to TA panic.

E/TC:? 0 TA panicked with code 0xffff0009
.....
E/TC:? 0 Call stack:
E/TC:? 0  0x000000004002f2f8 TEE_OpenPersistentObject at
lib/libutee/tee_api_objects.c:422

In this particular case TEE_ERROR_STORAGE_NOT_AVAILABLE is more suitable
than TEE_ERROR_NOT_IMPLEMENTED, as it provides to a TA a possibility
to handle this error code [1].

>From GPD TEE Internal Core specification [2]:
TEE_ERROR_STORAGE_NOT_AVAILABLE - if the persistent object is stored in a
storage area which is currently inaccessible. It may be associated with
the device but unplugged, busy, or inaccessible for some other reason.

[1]: 94db01ef44/lib/libutee/tee_api_objects.c (L419)
[2]: https://globalplatform.org/wp-content/uploads/2018/06/GPD_TEE_Internal_Core_API_Specification_v1.1.2.50_PublicReview.pdf

Signed-off-by: Igor Opaniuk <igor.opaniuk@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/optee/supplicant.c

@@ -82,8 +82,8 @@ void optee_suppl_cmd(struct udevice *dev, struct tee_shm *shm_arg,
 		cmd_shm_free(arg);
 		break;
 	case OPTEE_MSG_RPC_CMD_FS:
-		debug("OPTEE_MSG_RPC_CMD_FS not implemented\n");
-		arg->ret = TEE_ERROR_NOT_IMPLEMENTED;
+		debug("REE FS storage isn't available\n");
+		arg->ret = TEE_ERROR_STORAGE_NOT_AVAILABLE;
 		break;
 	case OPTEE_MSG_RPC_CMD_RPMB:
 		optee_suppl_cmd_rpmb(dev, arg);

include/tee.h

@@ -34,6 +34,7 @@
  * struct tee_version_data::gen_caps
  */
 #define TEE_SUCCESS			0x00000000
+#define TEE_ERROR_STORAGE_NOT_AVAILABLE	0xf0100003
 #define TEE_ERROR_GENERIC		0xffff0000
 #define TEE_ERROR_BAD_PARAMETERS	0xffff0006
 #define TEE_ERROR_ITEM_NOT_FOUND	0xffff0008