Fused GEMM+GEMM (#351)

* initial stub for gemm_gemm_xdl_cshuffle

* set up example code

* compiles

* prevent integer overflow

* harmonize interface between ref_gemm and ref_batched_gemm

* batched_gemm_gemm

* fix example

* host tensor gen: diagonal pattern in lowest two-dimensions only

* make c descriptors containing only integral constants

* clean up

* add BlockwiseGemmXdlops_v2 while exploring an unified approach

* implement proper interface

* tidy up example

* fix compilation warnings

* coarsely controlled 2nd gemm padding

* remove rocm-cmake's hard requirement for certain revision

* clang-format

* resolve merge conflict

* fix compilation error on gfx10

* adds acc0 elementwise op to interface

* add gemm_gemm instances and tests

* avoid LDS data hazard

* fix build

Co-authored-by: Chao Liu <chao.liu2@amd.com>

[ROCm/composable_kernel commit: c20a75b07d]

include/ck/tensor_operation/gpu/block/blockwise_gemm_xdlops_skip_b_lds.hpp

@@ -1,5 +1,7 @@
-#ifndef CK_BLOCKWISE_GEMM_XDLOPS_B_REGISTER_HPP
-#define CK_BLOCKWISE_GEMM_XDLOPS_B_REGISTER_HPP
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2018-2022, Advanced Micro Devices, Inc. All rights reserved.
+
+#pragma once
 
 #include "ck/utility/common_header.hpp"
 #include "ck/tensor_operation/gpu/thread/threadwise_tensor_slice_transfer.hpp"
@@ -317,4 +319,3 @@ struct BlockwiseGemmXdlops_k0mk1_k0nk1_m0n0m1n1m2m3m4n2_v1r1
 };
 
 } // namespace ck
-#endif