fix compiler error in "WITH_MKL"

Author: luotao1

CMakeLists.txt

@@ -109,7 +109,7 @@ else()
 endif()
 
 set(WITH_MKLML ${WITH_MKL})
-if (WITH_MKL AND ${AVX2_FOUND})
+if (WITH_MKL AND AVX2_FOUND)
     set(WITH_MKLDNN ON)
 else()
     message(STATUS "Do not have AVX2 intrinsics and disabled MKL-DNN")