dtoc: Support properties containing multiple phandle values

At present dtoc has a very simplistic view of phandles. It assumes that
a property has only a single phandle with a single argument (i.e. two
cells per property).

This is not true in many cases. Enhance the implementation to scan all
phandles in a property and to use the correct number of arguments (which
can be 0, 1, 2 or more) when generating the C code. For the struct
definitions, use a struct which can hold the maximum number of arguments
used by the property.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Kever Yang <kever.yang@rock-chips.com>

include/dt-structs.h

@@ -18,6 +18,11 @@ struct phandle_1_arg {
 	const void *node;
 	int arg[1];
 };
+
+struct phandle_2_arg {
+	const void *node;
+	int arg[2];
+};
 #include <generated/dt-structs.h>
 #endif