ide: refuse WIN_READ_NATIVE_MAX on empty device

What is the highest addressable sector on an empty CD-ROM?  Nothing is
addressable so produce an error.

This patch prevents a divide-by-zero in ide_set_sector() since
s->sectors and s->heads would be 0.  Not to mention that a sector=-1
argument would be nonsense.

Note that WIN_READ_NATIVE_MAX can be triggered using hdparm -N 1024
/dev/cdrom.  The LBA bit will be set to 1 though, so the only easy way
to go down the ide_set_sector() CHS code path which divides by zero is
to comment out the s->select & 0x40 case for testing.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
