Support ePAPR compliant phandle properties

Currently, the Linux kernel, libfdt and dtc, when using flattened
device trees encode a node's phandle into a property named
"linux,phandle".  The ePAPR specification, however - aiming as it is
to not be a Linux specific spec - requires that phandles be encoded in
a property named simply "phandle".

This patch adds support for this newer approach to dtc and libfdt.
Specifically:

	- fdt_get_phandle() will now return the correct phandle if it
          is supplied in either of these properties

	- fdt_node_offset_by_phandle() will correctly find a node with
          the given phandle encoded in either property.

	- By default, when auto-generating phandles, dtc will encode
          it into both properties for maximum compatibility.  A new -H
          option allows either only old-style or only new-style
          properties to be generated.

	- If phandle properties are explicitly supplied in the dts
	  file, dtc will not auto-generate ones in the alternate format.

	- If both properties are supplied, dtc will check that they
          have the same value.

	- Some existing testcases are updated to use a mix of old and
          new-style phandles, partially testing the changes.

	- A new phandle_format test further tests the libfdt support,
          and the -H option.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

tests/Makefile.tests

@@ -10,7 +10,8 @@ LIB_TESTS_L = get_mem_rsv \
 	sw_tree1 \
 	move_and_save mangle-layout nopulate \
 	open_pack rw_tree1 set_name setprop del_property del_node \
-	string_escapes references path-references boot-cpuid incbin \
+	string_escapes references path-references phandle_format \
+	boot-cpuid incbin \
 	extra-terminating-null \
 	dtbs_equal_ordered \
 	add_subnode_with_nops path_offset_aliases