Use the RTC optimizations when in high bitdepth mode.

Change 72193 made the encoder behave differently
when configured with and without high bitdepth.
This change means the same algorithm is used for both.

Change-Id: I707a44a94afca773a9e0c2f7ebeeea83030257c5
Merge "Use the RTC optimizations when in high bitdepth mode."