[serialization_lib] Fix Clamp and Pad Attributes

This patch implements following changes to attribute fields:
- PadAttribute: delete padding field, replace pad_const_int
	and pad_const_fp fields by pad_const, a field of
	ubyte array
- ClampAttribute: replace min_int, max_int, min_fp and max_fp
	fields by min_val and max_val, fields of ubyte arrays
- RescaleAttribute: delete multiplier and shift fields

Signed-off-by: Tai Ly <tai.ly@arm.com>
Change-Id: I5b075d29677cffca9ff2292708141d48410e7e72
diff --git a/schema/tosa.fbs b/schema/tosa.fbs
index 2bb3470..028765d 100644
--- a/schema/tosa.fbs
+++ b/schema/tosa.fbs
@@ -182,9 +182,7 @@
 }
 
 table PadAttribute {
-  padding: [int32];
-  pad_const_int: int32;
-  pad_const_fp: [ubyte] (force_align: 8);
+  pad_const: [ubyte] (force_align: 8);
 }
 
 table AxisAttribute {
@@ -199,17 +197,13 @@
 }
 
 table ClampAttribute {
-  min_int: int32;
-  max_int: int32;
-  min_fp: [ubyte] (force_align: 8);
-  max_fp: [ubyte] (force_align: 8);
+  min_val: [ubyte] (force_align: 8);
+  max_val: [ubyte] (force_align: 8);
 }
 
 table RescaleAttribute {
   input_zp: int32;
   output_zp: int32;
-  multiplier: [int32];
-  shift: [int32];
   scale32: bool;
   double_round: bool;
   per_channel: bool;