checkpatch: macros which define structure members are not complex

We often see macros which define structure members, these are not complex
and necessarily do not have braces or brackets.  For example:

    #define _PLIST_HEAD_INIT(head)                      \
        .prio_list = LIST_HEAD_INIT((head).prio_list),  \
        .node_list = LIST_HEAD_INIT((head).node_list)

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>