IVGCVSW-3235 Add scalar to use as padding value in Reference Pad

Signed-off-by: David Monahan <david.monahan@arm.com>
Change-Id: If050f318fcb7626bbfae1b8737a1d232a4a5a915
diff --git a/src/armnnSerializer/ArmnnSchema.fbs b/src/armnnSerializer/ArmnnSchema.fbs
index 83275ca..7969d10 100644
--- a/src/armnnSerializer/ArmnnSchema.fbs
+++ b/src/armnnSerializer/ArmnnSchema.fbs
@@ -409,6 +409,7 @@
 
 table PadDescriptor {
     padList:[uint];
+    padValue:float = 0;
 }
 
 table RsqrtLayer {