build: fix clang-format-diff[.py] detection

Fix clang-format-diff autodetection error in case of non-standard
clang-format-diff path. Also allow finding clang-format-diff.py in
non-standard location.

Type: improvement
Signed-off-by: Klement Sekera <klement.sekera@gmail.com>
Change-Id: I3cb76aa152a8245e62db62f5fe2ba96b1ff86428
diff --git a/extras/scripts/checkstyle.sh b/extras/scripts/checkstyle.sh
index 4dcf778..f26dc23 100755
--- a/extras/scripts/checkstyle.sh
+++ b/extras/scripts/checkstyle.sh
@@ -60,9 +60,12 @@
 if command -v clang-format-diff${SUFFIX} &> /dev/null;
 then
     CLANG_FORMAT_DIFF=clang-format-diff${SUFFIX}
+elif command -v clang-format-diff.py &> /dev/null;
+then
+    CLANG_FORMAT_DIFF=clang-format-diff.py
 elif command -v clang-format-diff &> /dev/null;
 then
-    CLANG_FORMAT=clang-format-diff
+    CLANG_FORMAT_DIFF=clang-format-diff
 elif [ ! -f $CLANG_FORMAT_DIFF ] ;
 then
     echo "*******************************************************************"