[serialization_lib] Add acc_type to Conv Attrs

This adds acc_type to ConvAttribute and TransposeConvAttribute

Signed-off-by: Tai Ly <tai.ly@arm.com>
Change-Id: I73bab71b2eb90f6451fadee21d5bed1811ecbfd7
diff --git a/schema/tosa.fbs b/schema/tosa.fbs
index 028765d..79b83b1 100644
--- a/schema/tosa.fbs
+++ b/schema/tosa.fbs
@@ -170,6 +170,7 @@
   input_zp: int32;
   weight_zp: int32;
   local_bound: bool;
+  acc_type: DType;
 }
 
 table TransposeConvAttribute {
@@ -179,6 +180,7 @@
   input_zp: int32;
   weight_zp: int32;
   local_bound: bool;
+  acc_type: DType;
 }
 
 table PadAttribute {