[AMDGPU, RISCV] Fix warnings

This patch fixes:

  llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp:451:13:
  error: explicit specialization cannot have a storage class
  [-Werror,-Wexplicit-specialization-storage-class]

  llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp:452:13:
  error: explicit specialization cannot have a storage class
  [-Werror,-Wexplicit-specialization-storage-class]

  llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp:454:1:
  error: explicit specialization cannot have a storage class
  [-Werror,-Wexplicit-specialization-storage-class]

  llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp:456:1:
  error: explicit specialization cannot have a storage class
  [-Werror,-Wexplicit-specialization-storage-class]

While I am at it, this patch changes the storage types of InsnBitWidth
specilization to "inline constexpr" to avoid linker errors.

Author: kazutakahirata

llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp

@@ -448,12 +448,12 @@ static DecodeStatus decodeVersionImm(MCInst &Inst, unsigned Imm,
 #include "AMDGPUGenDisassemblerTables.inc"
 
 // Define bitwidths for various types used to instantiate the decoder.
-template <> static constexpr uint32_t llvm::MCD::InsnBitWidth<uint32_t> = 32;
-template <> static constexpr uint32_t llvm::MCD::InsnBitWidth<uint64_t> = 64;
+template <> inline constexpr uint32_t llvm::MCD::InsnBitWidth<uint32_t> = 32;
+template <> inline constexpr uint32_t llvm::MCD::InsnBitWidth<uint64_t> = 64;
 template <>
-static constexpr uint32_t llvm::MCD::InsnBitWidth<std::bitset<96>> = 96;
+inline constexpr uint32_t llvm::MCD::InsnBitWidth<std::bitset<96>> = 96;
 template <>
-static constexpr uint32_t llvm::MCD::InsnBitWidth<std::bitset<128>> = 128;
+inline constexpr uint32_t llvm::MCD::InsnBitWidth<std::bitset<128>> = 128;
 
 //===----------------------------------------------------------------------===//
 //

llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp

@@ -702,10 +702,10 @@ static constexpr DecoderListEntry DecoderList32[]{
 };
 
 // Define bitwidths for various types used to instantiate the decoder.
-template <> constexpr uint32_t llvm::MCD::InsnBitWidth<uint16_t> = 16;
-template <> constexpr uint32_t llvm::MCD::InsnBitWidth<uint32_t> = 32;
+template <> inline constexpr uint32_t llvm::MCD::InsnBitWidth<uint16_t> = 16;
+template <> inline constexpr uint32_t llvm::MCD::InsnBitWidth<uint32_t> = 32;
 // Use uint64_t to represent 48 bit instructions.
-template <> constexpr uint32_t llvm::MCD::InsnBitWidth<uint64_t> = 48;
+template <> inline constexpr uint32_t llvm::MCD::InsnBitWidth<uint64_t> = 48;
 
 DecodeStatus RISCVDisassembler::getInstruction32(MCInst &MI, uint64_t &Size,
                                                  ArrayRef<uint8_t> Bytes,