[MTD-NAND] Add private data pointer. (#5974)

* Disable TRNG function in default configuration.

* Fix building issue

* To catch context of upper file system.

Co-authored-by: Wayne Lin <wclin@nuvoton.com>

components/drivers/include/drivers/mtd_nand.h

@@ -47,7 +47,10 @@ struct rt_mtd_nand_device
 
     /* operations interface */
     const struct rt_mtd_nand_driver_ops *ops;
+
+    void *priv;
 };
+typedef struct rt_mtd_nand_device* rt_mtd_nand_t;
 
 struct rt_mtd_nand_driver_ops
 {