Add TENSOR_QUANT8_ASYMM_SIGNED support for pooling ops

* Update AVERAGE_POOL_2D and MAX_POOL_2D

Bug: 143934716
Bug: 143934303
Test: quantization coupling tests in CTS and VTS
Change-Id: I15f36d6f819c92f96a46c40f9cc1491627644278
2 files changed