V4L/DVB (4927): Enhancements on usbvision driver

Enhance the buffer management of this driver + some corrections
- linux list.h usage for buffer management
- VIDIOC_ENUMSTD/VIDIOC_G_STD/VIDIOC_S_STD simplification (use of
v4l2_video_std_construct)
- create_sysfs : remove of warnings for video_device_create_file return code
- make the driver compatible with 2.6.19 kernel version (remove
slave_send and slave_recv in usbvision-i2c, change ctrlUrb_complete
function prototype)
- deactivated v4l2_read because this code was not the priority but
working on it :)

Signed-off-by: Thierry MERLE <thierry.merle@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>