aom_dsp: Remove empty CMake target.

Change-Id: I6e79d605818806005b65197745ca1bb66efb3890

aom_dsp/aom_dsp.cmake

diff --git a/aom_dsp/aom_dsp.cmake b/aom_dsp/aom_dsp.cmake
index 08dea4e..7c53953 100644
--- a/aom_dsp/aom_dsp.cmake
+++ b/aom_dsp/aom_dsp.cmake
@@ -444,8 +444,6 @@
              ${AOM_DSP_ENCODER_ASM_SSSE3_X86_64})
       endif ()
       add_asm_library("aom_dsp_encoder_ssse3" "AOM_DSP_ENCODER_ASM_SSSE3" "aom")
-      add_intrinsics_object_library("-mssse3" "ssse3" "aom_dsp_encoder"
-                                    "AOM_DSP_ENCODER_INTRIN_SSSE3")
     endif ()
   endif ()