Change default value for draft version

Default draft = True means that a TOSA flatbuffer with
no value stored for the draft flag is true.
Serialized TOSA with draft = False are release versions.

Signed-off-by: Eric Kunze <eric.kunze@arm.com>
Change-Id: I1304292ef83008a61a2a72e03171d00d5fe13442
diff --git a/schema/tosa.fbs b/schema/tosa.fbs
index 449c4ea..eeed385 100644
--- a/schema/tosa.fbs
+++ b/schema/tosa.fbs
@@ -270,7 +270,7 @@
   _major: int32 = -1;
   _minor: int32 = -1;
   _patch: int32 = -1;
-  _draft: bool = 255;
+  _draft: bool = true;
 }
 
 table TosaTensor {