dm: add support for DM_DEV_ARM_POLL

dm: add support for DM_DEV_ARM_POLL

Added in Linux commit v4.13-rc1~137^2~14.

* dm.c [!DM_LIST_VERSIONS] (DM_LIST_VERSIONS): Add leading zero.
[!DM_TARGET_MSG] (DM_TARGET_MSG): Likewise.
[!DM_DEV_SET_GEOMETRY_CMD] (DM_DEV_SET_GEOMETRY_CMD): Likewise.
[!DM_DEV_ARM_POLL] (DM_DEV_ARM_POLL): New macro.
(dm_ioctl_has_params, dm_ioctl): Handle DM_DEV_ARM_POLL.
* tests/ioctl_dm.c [!DM_DEV_ARM_POLL] (DM_DEV_ARM_POLL): New macro.
(main) <dummy_check_cmds>: Add DM_DEV_ARM_POLL.