Add yyerrorf() for formatted error messages.

Signed-off-by: Scott Wood <scottwood@freescale.com>

dtc-parser.y

@@ -307,15 +307,25 @@ label:
 
 %%
 
-void yyerror (char const *s)
+void yyerrorf(char const *s, ...)
 {
 	const char *fname = srcpos_filename_for_num(yylloc.filenum);
+	va_list va;
+	va_start(va, s);
 
 	if (strcmp(fname, "-") == 0)
 		fname = "stdin";
 
-	fprintf(stderr, "%s:%d %s\n",
-		fname, yylloc.first_line, s);
+	fprintf(stderr, "%s:%d ", fname, yylloc.first_line);
+	vfprintf(stderr, s, va);
+	fprintf(stderr, "\n");
+
+	va_end(va);
+}
+
+void yyerror (char const *s)
+{
+	yyerrorf("%s", s);
 }
 
 unsigned long long eval_literal(const char *s, int base, int bits)

srcpos.h

@@ -63,6 +63,7 @@ typedef struct YYLTYPE {
 
 
 extern void yyerror(char const *);
+extern void yyerrorf(char const *, ...) __attribute__((format(printf, 1, 2)));
 
 extern int srcpos_filenum;
 

treesource.c

@@ -23,7 +23,6 @@
 
 extern FILE *yyin;
 extern int yyparse(void);
-extern void yyerror(char const *);
 
 struct boot_info *the_boot_info;