aom_dsp: Remove empty CMake target.
aom_dsp: Remove empty CMake target.

Change-Id: I6e79d605818806005b65197745ca1bb66efb3890

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