core/hle/result: Relocate IPC error code to ipc_helpers

Relocates the error code to where it's most related, similar to how all
the other error codes are. Previously we were including a non-generic
error in the main result code header.

src/core/hle/ipc_helpers.h

@@ -19,9 +19,12 @@
 #include "core/hle/kernel/hle_ipc.h"
 #include "core/hle/kernel/object.h"
 #include "core/hle/kernel/server_session.h"
+#include "core/hle/result.h"
 
 namespace IPC {
 
+constexpr ResultCode ERR_REMOTE_PROCESS_DEAD{ErrorModule::HIPC, 301};
+
 class RequestHelperBase {
 protected:
     Kernel::HLERequestContext* context = nullptr;