ide: ide-atapi: fix compile error with defining macro DEBUG

ide: ide-atapi: fix compile error with defining macro DEBUG

Compile ide-atapi failed with defining macro "DEBUG"
...
|drivers/ide/ide-atapi.c:285:52: error: 'struct request' has
no member named 'cmd'; did you mean 'csd'?
|  debug_log("%s: rq->cmd[0]: 0x%x\n", __func__, rq->cmd[0]);
...

Since we split the scsi_request out of struct request, it missed
do the same thing on debug_log

Fixes: a91f780c1d92 ("block: split scsi_request out of struct request")
Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>