add PCF8574(A) port expander as passive 4x4 keyboard

src/input/peMatrixImpl.cpp

@@ -0,0 +1,16 @@
+#include "peMatrixImpl.h"
+#include "InputBroker.h"
+
+PeMatrixImpl *peMatrixImpl;
+
+PeMatrixImpl::PeMatrixImpl() : PeMatrixBase("matrixPE") {}
+
+void PeMatrixImpl::init()
+{
+    if (kb_model != 0x12) {
+        disable();
+        return;
+    }
+
+    inputBroker->registerSource(this);
+}