arm: init: export prev_bl_fdt_addr

When booting U-Boot on board with a locked down first-stage bootloader,
we emulate the Linux boot header. By passing the U-Boot FDT through this
first-stage bootloader and retrieving it afterwards we can pre-populate
the memory nodes and other info like the KASLR address.

Add a function to export the FDT addr so that boards can use it over the
built-in FDT.

Don't check is_addr_accessible() here because we might not yet have a
valid mem_map if it's going to be populated from the FDT, let the board
do their own validation instead.

Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Sumit Garg <sumit.garg@linaro.org> #qcs404
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
diff --git a/arch/arm/lib/save_prev_bl_data.c b/arch/arm/lib/save_prev_bl_data.c
index f7b23fa..b286bac 100644
--- a/arch/arm/lib/save_prev_bl_data.c
+++ b/arch/arm/lib/save_prev_bl_data.c
@@ -45,6 +45,11 @@
 	return false;
 }
 
+phys_addr_t get_prev_bl_fdt_addr(void)
+{
+	return reg0;
+}
+
 int save_prev_bl_data(void)
 {
 	struct fdt_header *fdt_blob;