VGA: Add input_ready() and readch() stubs

To use VGAConsole class, add empty input_ready() and readch().

Signed-off-by: Takuya ASADA <syuu@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

drivers/vga.cc

@@ -44,3 +44,13 @@ void VGAConsole::newline()
     }
     _col = 0;
 }
+
+bool VGAConsole::input_ready()
+{
+    return false;
+}
+
+char VGAConsole::readch()
+{
+    return 0;
+}

drivers/vga.hh

@@ -17,6 +17,8 @@ public:
     explicit VGAConsole(sched::thread* consumer, const termios *tio);
     virtual void write(const char *str, size_t len);
     virtual void newline();
+    virtual bool input_ready();
+    virtual char readch();
 private:
     unsigned _col = 0;
     static const unsigned ncols = 80, nrows = 25;