Replace FDT_VERSION() with stringify()

The FDT_VERSION() and _FDT_VERSION() macros don't really have anything
specific to do with the fdt version.  Rather, they're the common CPP
"stringify" idiom.  Move to util.h and rename to stringify() to
reflect this.

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

util.h

@@ -35,6 +35,9 @@
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
 
+#define stringify(s)	stringify_(s)
+#define stringify_(s)	#s
+
 static inline void NORETURN PRINTF(1, 2) die(const char *str, ...)
 {
 	va_list ap;