core: rework how we validate DeviceAllow= settings

Let's make sure we don't validate "char-*" and "block-*" expressions as
paths.

src/basic/path-util.h

@@ -147,7 +147,9 @@ char *file_in_same_dir(const char *path, const char *filename);
 bool hidden_or_backup_file(const char *filename) _pure_;
 
 bool is_device_path(const char *path);
-bool is_deviceallow_pattern(const char *path);
+
+bool valid_device_node_path(const char *path);
+bool valid_device_allow_pattern(const char *path);
 
 int systemd_installation_has_version(const char *root, unsigned minimal_version);