#472 disk.c fail to 'render' tracks from some plain cpc files

[Gergely Szasz]

Some Steven Flanagan disk cannot load:
Chance in Hell, A (2011)(Flanagan, Steven)(+3).dsk
Chance in Hell, A (2011)(Flanagan, Steven)(+3)[a].dsk
Cyborg 2900 (2011)(Flanagan, Steven)(+3)(GB)(de).dsk
Time Crystal, The (2011)(Flanagan, Steven)(+3).dsk

In disk.c we try to use the information of Data Rate in Track Info block wich only valid for Extended CPC files.
http://www.cpcwiki.eu/index.php/Format:DSK_disk_image_file_format#TRACK_INFORMATION_BLOCK_2

Related to [bugs:#450]

[Gergely Szasz]

This patch fix the bug.
Now we set Data Rate and Recording mode. with default value when parsing a plain CPC disk.