lib: Move fp_dev definition and helpers to separate header

libfprint/fpi-dev.h

@@ -0,0 +1,28 @@
+/*
+ * fp_dev types manipulation
+ * Copyright (C) 2018 Bastien Nocera <hadess@hadess.net>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+struct fp_dev;
+
+/**
+ * fp_img_dev:
+ *
+ * #fp_img_dev is an opaque structure type. You must access it using the
+ * appropriate functions.
+ */
+struct fp_img_dev;