Added missing AVX intrinsics for fp16: in particular, implemented predux which is required by the matrix-vector code.
Added missing AVX intrinsics for fp16: in particular, implemented predux which is required by the matrix-vector code.

ROCmSoftwarePlatform/hipeigen,ritsu1228/eigen,pasuka/eigen,ROCmSoftwarePlatform/hipeigen,ritsu1228/eigen,pasuka/eigen,pasuka/eigen,ritsu1228/eigen,ROCmSoftwarePlatform/hipeigen,ROCmSoftwarePlatform/hipeigen,pasuka/eigen,ritsu1228/eigen,pasuka/eigen,ritsu1228/eigen