IDE is a bit ugly in this respect.  For one it doesn't really keep track
of a sector size - most of the protocol is in units of 512 bytes, and we
assume 2048 bytes for CDROMs which is correct most of the time.

Second IDE allocates an I/O buffer long before we know if we're dealing
with a CDROM or not, so increase the alignment for the io_buffer
unconditionally.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>