simpleperf: enable .clang-format

Use the 2-space configuration by default and disable any formatting for
the demo/ subdirectory. The following command was used to generate this
change:

  $ find . \( -name \*.cpp -o -name \*.h \) -exec clang-format \
    --style=file -i {} \;

Test: mm
Change-Id: I89ec1f18f6e352f40cfa1a770087f3b586b1d7cb
diff --git a/simpleperf/nonlinux_support/nonlinux_support.cpp b/simpleperf/nonlinux_support/nonlinux_support.cpp
index b813109..65c82d3 100644
--- a/simpleperf/nonlinux_support/nonlinux_support.cpp
+++ b/simpleperf/nonlinux_support/nonlinux_support.cpp
@@ -17,9 +17,9 @@
 // Add fake functions to build successfully on darwin.
 #include <android-base/logging.h>
 
-#include "read_dex_file.h"
-#include "environment.h"
 #include "OfflineUnwinder.h"
+#include "environment.h"
+#include "read_dex_file.h"
 
 bool GetKernelBuildId(BuildId*) {
   return false;