fconf: Add dynamic config DTBs info as property

This patch introduces a better separation between the trusted-boot
related properties, and the dynamic configuration DTBs loading
information.

The dynamic configuration DTBs properties are moved to a new node:
`dtb-registry`. All the sub-nodes present will be provided to the
dynamic config framework to be loaded. The node currently only contains
the already defined configuration DTBs, but can be extended for future
features if necessary.
The dynamic config framework is modified to use the abstraction provided
by the fconf framework, instead of directly accessing the DTBs.

The trusted-boot properties are kept under the "arm,tb_fw" compatible
string, but in a separate `tb_fw-config` node.
The `tb_fw-config` property of the `dtb-registry` node simply points
to the load address of `fw_config`, as the `tb_fw-config` is currently
part of the same DTB.

Change-Id: Iceb6c4c2cb92b692b6e28dbdc9fb060f1c46de82
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>
diff --git a/plat/arm/board/juno/jmptbl.i b/plat/arm/board/juno/jmptbl.i
index 6ccdd28..b1b9ed4 100644
--- a/plat/arm/board/juno/jmptbl.i
+++ b/plat/arm/board/juno/jmptbl.i
@@ -20,6 +20,8 @@
 fdt     fdt_check_header
 fdt     fdt_node_offset_by_compatible
 fdt     fdt_setprop_inplace_namelen_partial
+fdt     fdt_first_subnode
+fdt     fdt_next_subnode
 mbedtls mbedtls_asn1_get_alg
 mbedtls mbedtls_asn1_get_alg_null
 mbedtls mbedtls_asn1_get_bitstring_null