atapi: kill MODE SENSE(6), fix MODE SENSE(10)

atapi: kill MODE SENSE(6), fix MODE SENSE(10)

Mode page 2A of emulated ATAPI DVD-ROM should have page length 0x14
like SCSI CD-ROM, rather than 0x12.

Mode page length is off by 8, as it should contain the length of the
payload after the first two bytes.

MODE SENSE(6) should be thrown out of ATAPI DVD-ROM emulation.  It is
not specified in the ATAPI list of MMC-2, and MMC-5 prescribes to use
MODE SENSE(10).  Anyway, its implementation is wrong.

Reported-by: Thomas Schmitt <scdbackup@gmx.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>