ide-scsi: remove kmalloced struct request

This converts ide-scsi to use blk_get/put_request instead of
kmalloc/kfree.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>