block: Switch struct packet_command to use struct scsi_sense_hdr

There is a lot of needless struct request_sense usage in the CDROM
code. These can all be struct scsi_sense_hdr instead, to avoid any
confusion over their respective structure sizes. This patch is a lot
of noise changing "sense" to "sshdr", but the final code is more
readable to distinguish between "sense" meaning "struct request_sense"
and "sshdr" meaning "struct scsi_sense_hdr".

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/include/linux/cdrom.h b/include/linux/cdrom.h
index e75dfd1..528271c 100644
--- a/include/linux/cdrom.h
+++ b/include/linux/cdrom.h
@@ -13,6 +13,7 @@
 
 #include <linux/fs.h>		/* not really needed, later.. */
 #include <linux/list.h>
+#include <scsi/scsi_common.h>
 #include <uapi/linux/cdrom.h>
 
 struct packet_command
@@ -21,7 +22,7 @@
 	unsigned char 		*buffer;
 	unsigned int 		buflen;
 	int			stat;
-	struct request_sense	*sense;
+	struct scsi_sense_hdr	*sshdr;
 	unsigned char		data_direction;
 	int			quiet;
 	int			timeout;