opencl: add optimized q8_0 mm kernel for adreno (llama/18871)

opencl: add optimized q8_0 mm kernel for adreno (llama/18871)

* Add Q8_0 OpenCL kernel

Co-authored-by: yunjie <redacted>
* opencl: fix build for non-adreno

* opencl: refactor q8_0

* opencl: enforce subgroup size of 64 for adreno for q8_0

* For A750 and older generations, subgroup size can be 64 or 128.
  This kernel assumes subgroup size 64.

* opencl: suppress warning when adreno kernels are disabled

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Co-authored-by: yunjie <redacted>
Co-authored-by: Li He <redacted>