drm_hwcomposer: clang-format: Preserve header blocks

Instruct clang-format to leave logical blocks of header formats intact,
which helps separate headers from the system, framework, external
libraries, and this project.

Change-Id: I06c1944097574c30ee05be671f6023ccd0a0d4b7
diff --git a/.clang-format b/.clang-format
index 984fa5e..caadedf 100644
--- a/.clang-format
+++ b/.clang-format
@@ -3,5 +3,6 @@
 AllowShortIfStatementsOnASingleLine: false
 AllowShortLoopsOnASingleLine: false
 AllowShortFunctionsOnASingleLine: None
+IncludeBlocks: Preserve
 PenaltyBreakAssignment: 10000000
 PenaltyBreakBeforeFirstCallParameter: 1000