fastmodel: add helper class for exporting amba_pv signal

To bridge amba_pv::signal_master_port<bool> with IntPins, we made a
helper class for the purpose. The SignalSender class can be exported as
a gem5 Port, receive the signal, and transfer to fastmodel.

Here's an example showing how it works

*.lisa
```
component
{
  slave port<Signal> reset;
}
```

evs.hh
```
class
{
  SignalSender reset;
}
```

evs.cc
```
constructor(Params &p) : reset(p.name + ".reset", 0)
{
  reset.signal_out.bind(Base::reset);
}

getPort
{
  return reset;
}
```

Change-Id: I0936f9ebb2cd60e975661ae78e590285da697771
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48943
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/fastmodel/common/signal_sender.hh

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2021 Google, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __ARCH_ARM_FASTMODEL_COMMON_SIGNAL_SENDER_HH__
+#define __ARCH_ARM_FASTMODEL_COMMON_SIGNAL_SENDER_HH__
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Woverloaded-virtual"
+#include <amba_pv.h>
+#pragma GCC diagnostic pop
+
+#include "dev/intpin.hh"
+
+namespace FastModel
+{
+
+class SignalSender : public IntSinkPinBase
+{
+  public:
+    amba_pv::signal_master_port<bool> signal_out;
+
+    SignalSender(const std::string &_name, PortID _id) :
+        IntSinkPinBase(_name, _id, 0),
+        signal_out((_name + ".sig").c_str())
+    {}
+
+  private:
+    void raiseOnDevice() override { signal_out.set_state(id, true); }
+    void lowerOnDevice() override { signal_out.set_state(id, false); }
+};
+
+} // namespace FastModel
+
+#endif  // __ARCH_ARM_FASTMODEL_COMMON_SIGNAL_SENDER_HH__