warp7: Specify a default CONFIG_OPTEE_LOAD_ADDR if non provided

If no CONFIG_OPTEE_LOAD_ADDR is provided i.e. you are not loading OPTEE
into memory in u-boot, then just set the non-existent CONFIG option to
zero, elsewise stringify(CONFIG_OPTEE_LOAD_ADDR) will return
"CONFIG_OPTEE_LOAD_ADDR" - which looks weird in the u-boot environment.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
diff --git a/include/configs/warp7.h b/include/configs/warp7.h
index 358941e..73541fe 100644
--- a/include/configs/warp7.h
+++ b/include/configs/warp7.h
@@ -34,6 +34,10 @@
 #define BOOT_SCR_STRING "source ${bootscriptaddr}\0"
 #endif
 
+#ifndef CONFIG_OPTEE_LOAD_ADDR
+#define CONFIG_OPTEE_LOAD_ADDR 0
+#endif
+
 #define CONFIG_EXTRA_ENV_SETTINGS \
 	CONFIG_DFU_ENV_SETTINGS \
 	"script=boot.scr\0" \