sync: fix sync scripts commit_signature function

After recent lint changes, commit_signature() function now gets optional
array of paths as multiple arguments, instead of entire array as second
argument. So adjust commit_signature() to handle this correctly.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

scripts/sync-kernel.sh

@@ -86,7 +86,9 @@ commit_desc()
 # $2 - paths filter
 commit_signature()
 {
-	git show --pretty='("%s")|%aI|%b' --shortstat $1 -- ${2-.} | tr '\n' '|'
+	local ref=$1
+	shift
+	git show --pretty='("%s")|%aI|%b' --shortstat $ref -- "${@-.}" | tr '\n' '|'
 }
 
 # Cherry-pick commits touching libbpf-related files