Update the clang-format file with latest

The latest clang format adds the IndentExternBlock property[1]

[1] https://github.com/openbmc/docs/blob/master/style/cpp/.clang-format

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I69d1a17de61c052193891cc9c009c54e68605022
diff --git a/.clang-format b/.clang-format
index d92a3f1..41f2211 100644
--- a/.clang-format
+++ b/.clang-format
@@ -78,6 +78,7 @@
   - Regex:           '.*'
     Priority:        6
 IndentCaseLabels: true
+IndentExternBlock: NoIndent
 IndentRequiresClause: true
 IndentWidth:     4
 IndentWrappedFunctionNames: true
@@ -126,4 +127,3 @@
 TabWidth:        4
 UseTab:          Never
 ...
-