Add a missing include
Add a missing include

This is for aom_memset16() used later in the code.

Change-Id: I4426354bae4f0bf2e3012a138a8e779098b35173

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom