Replace TENSOR_QUANT16_ASYMM with TENSOR_QUANT16_SYMM

* Update doc string
* Update zero point mutation to check for symmetric quantization

Fix: 118671831
Test: VtsHalNeuralnetworksV1_2TargetTest
Change-Id: Id1999c793c839b892cfe45cbb245611b12db2a72
Merged-In: Id1999c793c839b892cfe45cbb245611b12db2a72
(cherry picked from commit 48c8820bac243e7eaff680056f2145f1b3b1ab2a)
2 files changed