doc: botching-up-ioctls: Make it clearer why structs must be padded

This came up in discussions when reviewing drm patches.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
1 file changed