pdl: Skip unnecessary conforms method computations

This avoids a lint warning since the “>= 0” comparison is known to
always be true.

Test: atest pdl_tests
(cherry picked from https://android-review.googlesource.com/q/commit:6470489aa750201dd67fa71d99fa802869f5a02f)
Merged-In: I480c9a8e7ae499e2038eb5a9dd032521c14fe957
Change-Id: I480c9a8e7ae499e2038eb5a9dd032521c14fe957