ioctl: Rearrange members in nvme_lockdown_args

ioctl: Rearrange members in nvme_lockdown_args

Avoid any holes in the struct by rearranging the members. Also add the
attribute packed to struct definition to reduce ABI breakage.

struct nvme_lockdown_args {
        int                        args_size;            /*     0     4 */
        int                        fd;                   /*     4     4 */
        __u32 *                    result;               /*     8     8 */
        __u32                      timeout;              /*    16     4 */
        __u8                       scp;                  /*    20     1 */
        __u8                       prhbt;                /*    21     1 */
        __u8                       ifc;                  /*    22     1 */
        __u8                       ofi;                  /*    23     1 */
        __u8                       uuidx;                /*    24     1 */

        /* size: 32, cachelines: 1, members: 8 */
        /* padding: 1 */
        /* last cacheline: 32 bytes */
} __attribute__((__aligned__(8)));

Signed-off-by: Daniel Wagner <dwagner@suse.de>