cmd_mode_sense always reports 0x70, no CDROM present

cmd_mode_sense
  https://git.qemu.org/?p=qemu.git;a=blob;f=hw/ide/atapi.c;hb=refs/heads/master#l852
always reports 0x70 in byte 2 returned, indicating no CD-ROM present.

If CD-ROM is present, should report 0x01 (or 0x11).
If CD-ROM absent, should report 0x70.