Tegra: dummy support for the io_storage backend

This patch provides dummy macros and platform files to compile
the io_storage driver backend. This patch is necessary to
remove the "--unresolved=el3_panic" linker flag from Tegra's
makefiles and allow us to revert this workaround, previously
suggested by the ARM toolchain team.

The "--unresolved=el3_panic" flag actually was a big hammer that
allowed Tegra platforms to work with armlink previously but it
masks legit errors with the code as well.

Change-Id: I0421d35657823215229f84231896b84167f90548
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
diff --git a/plat/nvidia/tegra/common/tegra_common.mk b/plat/nvidia/tegra/common/tegra_common.mk
index d9eec4d..2a2f278 100644
--- a/plat/nvidia/tegra/common/tegra_common.mk
+++ b/plat/nvidia/tegra/common/tegra_common.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -22,6 +22,7 @@
 
 BL31_SOURCES		+=	drivers/console/aarch64/console.S		\
 				drivers/delay_timer/delay_timer.c		\
+				drivers/io/io_storage.c				\
 				${TEGRA_GICv2_SOURCES}				\
 				${COMMON_DIR}/aarch64/tegra_helpers.S		\
 				${COMMON_DIR}/drivers/pmc/pmc.c			\
@@ -29,6 +30,7 @@
 				${COMMON_DIR}/tegra_bl31_setup.c		\
 				${COMMON_DIR}/tegra_delay_timer.c		\
 				${COMMON_DIR}/tegra_fiq_glue.c			\
+				${COMMON_DIR}/tegra_io_storage.c		\
 				${COMMON_DIR}/tegra_platform.c			\
 				${COMMON_DIR}/tegra_pm.c			\
 				${COMMON_DIR}/tegra_sip_calls.c			\
diff --git a/plat/nvidia/tegra/common/tegra_io_storage.c b/plat/nvidia/tegra/common/tegra_io_storage.c
new file mode 100644
index 0000000..21641aa
--- /dev/null
+++ b/plat/nvidia/tegra/common/tegra_io_storage.c
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2019, NVIDIA Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <errno.h>
+#include <plat/common/platform.h>
+
+/*
+ * Return an IO device handle and specification which can be used to access
+ * an image. Use this to enforce platform load policy.
+ *
+ * This function is not supported at this time
+ */
+int plat_get_image_source(unsigned int image_id, uintptr_t *dev_handle,
+			  uintptr_t *image_spec)
+{
+	return -ENOTSUP;
+}