dtc: Simplify error handling for unparseable input

Currently, main() tests if it got a valid input tree from whichever
dt_from_*() function it invoked and if not, die()s.  For one thing,
this test has, for no good reason, three different ways for those
functions to communicate a failure to provide input (bi NULL, bi->dt
NULL, or bi->error non-zero).  For another, in every case save one, if
the dt_from_*() functions are unable to provide input they will
immediately die() (with a more specific error message) rather than
proceeding to the test in main().

Therefore, this patch removes this test, making the one case that
could have triggered it (in dt_from_source()) call die() directly
instead.  With this change, the error field in struct boot_info is now
unused, so remove it.

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

dtc.c

@@ -201,9 +201,6 @@ int main(int argc, char *argv[])
 	if (inf && inf->file != stdin)
 		fclose(inf->file);
 
-	if (! bi || ! bi->dt || bi->error)
-		die("Couldn't read input tree\n");
-
 	fill_fullpaths(bi->dt, "");
 	process_checks(force, bi);
 

dtc.h

@@ -232,7 +232,6 @@ struct reserve_info *add_reserve_entry(struct reserve_info *list,
 struct boot_info {
 	struct reserve_info *reservelist;
 	struct node *dt;		/* the device tree */
-	int error;
 };
 
 struct boot_info *build_boot_info(struct reserve_info *reservelist,

livetree.c

@@ -172,7 +172,6 @@ struct boot_info *build_boot_info(struct reserve_info *reservelist,
 	bi = xmalloc(sizeof(*bi));
 	bi->reservelist = reservelist;
 	bi->dt = tree;
-	bi->error = 0;
 
 	return bi;
 }

treesource.c

@@ -36,9 +36,11 @@ struct boot_info *dt_from_source(const char *fname)
 	yyin = srcpos_file->file;
 
 	if (yyparse() != 0)
-		return NULL;
+		die("Unable to parse input tree\n");
+
+	if (treesource_error)
+		die("Syntax error parsing input tree\n");
 
-	the_boot_info->error = treesource_error;
 	return the_boot_info;
 }