fix:rewrite to make code clearer

Close #I3S5W4

Change-Id: Iba7054a8abbcc5545c783a06411312c7a1c6075e

sys/dev/usb/serial/usb_serial.c

@@ -1351,7 +1351,8 @@ tty_usb_write_wait(void)
 static int
 tty_usb_open(struct file *filep)
 {
-	struct ucom_softc *sc = (struct ucom_softc *)((struct drv_data*)filep->f_vnode->data)->priv;
+	struct drv_data *drvData = (struct drv_data *)filep->f_vnode->data;
+	struct ucom_softc *sc = (struct ucom_softc *)drvData->priv;
 	int ret;
 
 	UCOM_MTX_LOCK(sc);
@@ -1369,7 +1370,8 @@ tty_usb_open(struct file *filep)
 static int
 tty_usb_close(struct file *filep)
 {
-	struct ucom_softc *sc = (struct ucom_softc *)((struct drv_data*)filep->f_vnode->data)->priv;
+	struct drv_data *drvData = (struct drv_data *)filep->f_vnode->data;
+	struct ucom_softc *sc = (struct ucom_softc *)drvData->priv;
 
 	UCOM_MTX_LOCK(sc);
 	tty_usb_queue_delete();
@@ -1382,7 +1384,8 @@ tty_usb_close(struct file *filep)
 static ssize_t
 tty_usb_read(struct file *filep, char *buffer, size_t buflen)
 {
-	struct ucom_softc *sc = (struct ucom_softc *)((struct drv_data*)filep->f_vnode->data)->priv;
+	struct drv_data *drvData = (struct drv_data *)filep->f_vnode->data;
+	struct ucom_softc *sc = (struct ucom_softc *)drvData->priv;
 	int read_len = -1;
 	int ret;
 	UCOM_MTX_LOCK(sc);
@@ -1440,7 +1443,8 @@ tty_usb_read(struct file *filep, char *buffer, size_t buflen)
 static ssize_t
 tty_usb_write(struct file *filep, const char *buffer, size_t buflen)
 {
-	struct ucom_softc *sc = (struct ucom_softc *)((struct drv_data*)filep->f_vnode->data)->priv;
+	struct drv_data *drvData = (struct drv_data *)filep->f_vnode->data;
+	struct ucom_softc *sc = (struct ucom_softc *)drvData->priv;
 
 	tx_data_copy_in(sc, (void *)buffer, buflen);
 	ucom_outwakeup(sc);

sys/dev/usb/usb_dev.c

@@ -781,7 +781,8 @@ usb_fifo_close(struct usb_fifo *f, int fflags)
 static int
 usb_open(struct file *filep)
 {
-	struct usb_fs_privdata* pd = (struct usb_fs_privdata*)((struct drv_data*)filep->f_vnode->data)->priv;
+	struct drv_data* drvData = (struct drv_data* )filep->f_vnode->data;
+	struct usb_fs_privdata* pd = (struct usb_fs_privdata* )drvData->priv;
 	struct usb_cdev_refdata refs;
 	struct usb_cdev_privdata *cpd = NULL;
 	int err;