Document that quantized PAD behavior is undefined before NNAPI 1.2

We had no tests for quantized PAD in NNAPI 1.1 and think that vendors might have implemented different behaviors.

Bug: 122243484
Test: N/A
Change-Id: Ibfc0801ab746fc271dc5f8efc764b818c6d49df4
Merged-In: Ibfc0801ab746fc271dc5f8efc764b818c6d49df4
(cherry picked from commit b01ce9644e3e46600143953905a9b53c0de37887)
3 files changed