[lldb] Include bit.h instead of SwapByteOrder.h (NFC) (llvm#151903)

We use llvm::byteswap from bit.h, but we don't use any feature from
SwapByteOrder.h.

Author: kazutakahirata

lldb/include/lldb/Core/Opcode.h

@@ -12,7 +12,7 @@
 #include "lldb/Utility/Endian.h"
 #include "lldb/lldb-enumerations.h"
 
-#include "llvm/Support/SwapByteOrder.h"
+#include "llvm/ADT/bit.h"
 
 #include <cassert>
 #include <cstdint>