nn: update disabled tests with justification comment

Investigating the disabled generated tests shows that they are failing
either due to the TFLite uprev or the need for hardware buffers.

BUG=b:159414785
TEST=FEATURES=test emerge-betty chromeos-base/aosp-frameworks-ml-nn

Change-Id: Icb8159bebb742aa99045ef5e944ddbcfe03b111b
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/frameworks/ml/+/2263753
Commit-Queue: Jim Pollock <jmpollock@chromium.org>
Tested-by: Jim Pollock <jmpollock@chromium.org>
Reviewed-by: Stuart Langley <slangley@chromium.org>
Auto-Submit: Jim Pollock <jmpollock@chromium.org>