Return a non-zero exit code if an error occurs during dts parsing.

Previously, only failure to parse caused the reading of the tree to fail;
semantic errors that called yyerror() but not YYERROR only emitted a message,
without signalling make to stop the build.

Signed-off-by: Scott Wood <scottwood@freescale.com>
diff --git a/treesource.c b/treesource.c
index e7d580f..980bda7 100644
--- a/treesource.c
+++ b/treesource.c
@@ -25,10 +25,12 @@
 extern int yyparse(void);
 
 struct boot_info *the_boot_info;
+int treesource_error;
 
 struct boot_info *dt_from_source(const char *fname)
 {
 	the_boot_info = NULL;
+	treesource_error = 0;
 
 	push_input_file(fname);
 
@@ -37,6 +39,7 @@
 
 	fill_fullpaths(the_boot_info->dt, "");
 
+	the_boot_info->error = treesource_error;
 	return the_boot_info;
 }