[tosa_mlir_translator] Use new Clamp and Pad fbs attributes

This implements changes required for new Tosa Flatbuffer
schema where Clamp and Pad attributes have changed to use
ubyte arrays to store int or float values.

Signed-off-by: Tai Ly <tai.ly@arm.com>
Change-Id: I2aa2025422fda4aacaf6d80727060a01a30cee89