libfdt: Fixups for 64-bit machines

The error encoding for pointers is incorrect on machines where
sizeof(int) != sizeof(void *), which includes most 64-bit platforms
(in particular, AMD64 and powerpc64).  This patch fixes it.

libfdt_internal.h

@@ -41,7 +41,7 @@ const char *_fdt_find_string(const char *strtab, int tabsize, const char *s);
 int _fdt_node_end_offset(struct fdt_header *fdt, int nodeoffset);
 
 #define OFFSET_ERROR(code)	-(code)
-#define PTR_ERROR(code)		(void *)(-(code))
+#define PTR_ERROR(code)		(void *)(-(long)(code))
 
 #define SW_MAGIC		(~FDT_MAGIC)