Get type (AT,XT2,XT286,CONV,PS)
        (harddisk only)

        Entry:
          AH = 15h
          DL = drive ID

        Return:
          AH = disk type
               0 = disk not there
               1 = floppy, no change detection present
               2 = floppy with change detection
               3 = fixed disk
          CX:DX = number of 512-byte sectors