Camera: Avoid duplicate zoom ratio entries

In case we have small enough max digital range, the
calculated zoom ratios might get truncated and reference
the same zoom value.
Check for any previous duplicates and skip the ratios if
needed.

Bug: 198414316
Test: atest -c cts/tests/camera/src/android/hardware/cts/CameraTest.java
Change-Id: If63169e9de6bc6d33e93ce1c1597e0d0a9813371