V4L/DVB (12800): tm6000: fix tm6000 analog video buffer handling

Previously, there were no sync between video buffer filling and received
URBs. So, the presented image were a mix of frame and frame-1. Now, a
filled buffer should contain only data for that frame.

allocates a maximum of 64 KB per each URB area. This fixed two bugs:

- Sometimes, there were no available continuos block of about 1 MB;
- Image weren't not properly updated, since parts of the URBs aren't
  updated.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/staging/tm6000/tm6000-usb-isoc.h

@@ -39,6 +39,13 @@ struct usb_isoc_ctl {
 		/* Last field: ODD or EVEN? */
 	int				field;
 
+		/* Stores incomplete commands */
 	u32				tmp_buf;
 	int				tmp_buf_len;
+
+		/* Stores already requested buffers */
+	struct tm6000_buffer    	*buf;
+
+		/* Stores the number of received fields */
+	int				nfields;
 };