[tosa_mlir_translator] Fix fp16, bf16 and fp8 serialization

Fix serialization and deserialization of fp16, bf16 and fp8
for pad_const, clamp min_val/max_val, and const values

Signed-off-by: Tai Ly <tai.ly@arm.com>
Change-Id: Ia39a17d2f395584d5555d2c86cdae7113cf14e3f