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: NAndy Whitcroft <apw@shadowen.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2155,6 +2155,7 @@ sub process {
 				if ($dstat ne '' &&
 				    $dstat !~ /^(?:$Ident|-?$Constant)$/ &&
 				    $dstat !~ /$exceptions/ &&
+				    $dstat !~ /^\.$Ident\s*=/ &&
 				    $dstat =~ /$Operators/)
 				{
 					ERROR("Macros with complex values should be enclosed in parenthesis\n" . "$here\n$ctx\n");