webnn: Enforce input data type constraints for conv2d
As specified in webmachinelearning/webnn#646
Bug: 328567884
Change-Id: I620653f574303e6f5b18d3b540b647f07e0cf64c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5492307
Reviewed-by: ningxin hu ningxin.hu@intel.com
Commit-Queue: Austin Sullivan asully@chromium.org
Cr-Commit-Position: refs/heads/main@{#1293407}