scripts/kallsyms: set relative_base more effectively

Currently, record_relative_base() iterates over the entire table to
find the minimum address, but it is not efficient because we sort
the table anyway.

After sort_symbol(), the table is sorted by address. (kallsyms parses
the 'nm -n' output, so the data is already sorted by address, but this
commit does not rely on it.)

Move record_relative_base() after sort_symbols(), and take the first
non-absolute symbol value.

scripts/kallsyms.c

@@ -746,11 +746,15 @@ static void record_relative_base(void)
 {
 	unsigned int i;
 
-	relative_base = -1ULL;
 	for (i = 0; i < table_cnt; i++)
-		if (!symbol_absolute(&table[i]) &&
-		    table[i].addr < relative_base)
+		if (!symbol_absolute(&table[i])) {
+			/*
+			 * The table is sorted by address.
+			 * Take the first non-absolute symbol value.
+			 */
 			relative_base = table[i].addr;
+			return;
+		}
 }
 
 int main(int argc, char **argv)
@@ -774,9 +778,9 @@ int main(int argc, char **argv)
 	shrink_table();
 	if (absolute_percpu)
 		make_percpus_absolute();
+	sort_symbols();
 	if (base_relative)
 		record_relative_base();
-	sort_symbols();
 	optimize_token_table();
 	write_src();