fix Implement ksu_wrapper_dedupe_file_range function

Added a new function for deduplicating file ranges.

kernel/file_wrapper.c

@@ -286,6 +286,7 @@ static int ksu_wrapper_clone_file_range(struct file *file_in, loff_t pos_in,
 	}
 	return -EINVAL;
 }
+#endif
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 19, 0)
 static int ksu_wrapper_dedupe_file_range(struct file *src_file, loff_t loff,
 				struct file *dst_file, loff_t dst_loff, u64 len) {
@@ -382,4 +383,4 @@ struct ksu_file_wrapper* ksu_create_file_wrapper(struct file* fp) {
 void ksu_delete_file_wrapper(struct ksu_file_wrapper* data) {
 	fput((struct file*) data->orig);
 	kfree(data);
-}
+}