[media] drivers/media/usb/{s2255drv.c, tm6000/tm6000-alsa.c, tm6000/tm6000-input.c}: Remove potential NULL dereferences

If the NULL test is necessary, the initialization involving a dereference of
the tested value should be moved after the NULL test.

The sematic patch that fixes this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
type T;
expression E;
identifier i,fld;
statement S;
@@

- T i = E->fld;
+ T i;
  ... when != E
      when != i
  if (E == NULL) S
+ i = E->fld;
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/usb/s2255/s2255drv.c

@@ -1861,11 +1861,12 @@ static int s2255_release(struct file *file)
 static int s2255_mmap_v4l(struct file *file, struct vm_area_struct *vma)
 {
 	struct s2255_fh *fh = file->private_data;
-	struct s2255_dev *dev = fh->dev;
+	struct s2255_dev *dev;
 	int ret;
 
 	if (!fh)
 		return -ENODEV;
+	dev = fh->dev;
 	dprintk(4, "%s, vma=0x%08lx\n", __func__, (unsigned long)vma);
 	if (mutex_lock_interruptible(&dev->lock))
 		return -ERESTARTSYS;