[PATCH] libata-dev: wait idle after reading the last data block

Some CD-ROM drives are slow to clear DRQ, after the last data block
is read by PIO. Use ata_wait_idle() after reading the last data block.

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>