webnn: Enforce data type constraints for averagePool2d and l2Pool2d
As specified in webmachinelearning/webnn#646
Bug: 328567884
Change-Id: If0ea256805b5cfebdf15e0727fbc91acab918bbb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5500424
Reviewed-by: Austin Sullivan asully@chromium.org
Auto-Submit: Shiyi Zou shiyi.zou@intel.com
Commit-Queue: Shiyi Zou shiyi.zou@intel.com
Reviewed-by: ningxin hu ningxin.hu@intel.com
Cr-Commit-Position: refs/heads/main@{#1297393}