cgenie: fix plain sector disk images

src/emu/bus/cgenie/expansion/floppy.c

@@ -5,8 +5,6 @@
     EACA Colour Genie Floppy Disc Controller
 
     TODO:
-    - Plain sector files are not working (some sectors are marked DDM),
-      maybe support the .cgd format?
     - What's the exact FD1793 model?
     - How does it turn off the motor?
     - What's the source of the timer and the exact timings?

src/lib/formats/cgenie_dsk.c

@@ -29,6 +29,16 @@ const char *cgenie_format::extensions() const
 	return "dsk";
 }
 
+int cgenie_format::get_track_dam_fm(const format &f, int head, int track)
+{
+	return (track == f.track_count/2) ? FM_DDAM : FM_DAM;
+}
+
+int cgenie_format::get_track_dam_mfm(const format &f, int head, int track)
+{
+	return (track == f.track_count/2) ? MFM_DDAM : MFM_DAM;
+}
+
 const cgenie_format::format cgenie_format::formats[] =
 {
 	{   //  102k 5 1/4 inch single density single sided (Type A)

src/lib/formats/cgenie_dsk.h

@@ -24,6 +24,10 @@ public:
 	virtual const char *description() const;
 	virtual const char *extensions() const;
 
+protected:
+	virtual int get_track_dam_fm(const format &f, int head, int track);
+	virtual int get_track_dam_mfm(const format &f, int head, int track);
+
 private:
 	static const format formats[];
 };