tools/checkpatch.sh: enhance added files judgement with +++ at the line beginning

In https://github.com/apache/incubator-nuttx-apps/pull/179, there is a
removed graphics/littlevgl/lv_symbol_def.patch file whose content would be
treated abnormally and results in errors.

Signed-off-by: liuhaitao <liuhaitao@xiaomi.com>

tools/checkpatch.sh

@@ -56,7 +56,7 @@ check_file() {
 
 check_ranges() {
   while read; do
-    if [[ $REPLY =~ \+\+\+\ (b/)?([^[:blank:]]+).* ]]; then
+    if [[ $REPLY =~ ^(\+\+\+\ (b/)?([^[:blank:]]+).*)$ ]]; then
       if [ "$ranges" != "" ]; then
         if [ $range != 0 ]; then
           check_file $ranges $path 2>&1
@@ -64,7 +64,7 @@ check_ranges() {
           check_file $path 2>&1
         fi
       fi
-      path=${BASH_REMATCH[2]}
+      path=${BASH_REMATCH[3]}
       ranges=""
     elif [[ $REPLY =~ @@\ -[0-9]+(,[0-9]+)?\ \+([0-9]+,[0-9]+)?\ @@.* ]]; then
       ranges+="-r ${BASH_REMATCH[2]} "