Disable IC3 IC4 Q8 XNNPACK (#871)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/871

We need a fix from quantizer; disable it for MVP but we can enable it for main branch later.

The issue is quantization scale difference due to calibration and XNNPACK won't execute the program; it only occurs when running it with both "--delegate" and "--quantize".

With portable kernel it executes.

Reviewed By: guangy10

Differential Revision: D50236323

fbshipit-source-id: b37cf0bb0294f9c7e65f945dc9c871e0b889b607