Support shared Mbed TLS heap for SGM

Change-Id: Ibbfedb6601feff51dfb82c1d94850716c5a36d24
Signed-off-by: John Tsichritzis <john.tsichritzis@arm.com>
diff --git a/plat/arm/css/sgm/fdts/sgm_tb_fw_config.dts b/plat/arm/css/sgm/fdts/sgm_tb_fw_config.dts
index 9502549..d481018 100644
--- a/plat/arm/css/sgm/fdts/sgm_tb_fw_config.dts
+++ b/plat/arm/css/sgm/fdts/sgm_tb_fw_config.dts
@@ -12,5 +12,16 @@
 		compatible = "arm,tb_fw";
 		hw_config_addr = <0x0 0x83000000>;
 		hw_config_max_size = <0x01000000>;
+		/*
+		 * The following two entries are placeholders for Mbed TLS
+		 * heap information. The default values don't matter since
+		 * they will be overwritten by BL1.
+		 * In case of having shared Mbed TLS heap between BL1 and BL2,
+		 * BL1 will populate these two properties with the respective
+		 * info about the shared heap. This info will be available for
+		 * BL2 in order to locate and re-use the heap.
+		 */
+		mbedtls_heap_addr = <0x0 0x0>;
+		mbedtls_heap_size = <0x0>;
 	};
 };