Fix encoder use of 16-bit operating path

When compiled with --disable-lowbitdepth, the decoder uses the generic
16-bit operating path, regardless of the input video profile.
The encoder should also use the generic 16-bit operating path if the
low-bitdepth operating path has been disabled at build time.

Change-Id: I421cc774b45d2c76bea8730cc8726224cb4aba1e
1 file changed