- SYSFS: Replaced all to_video_device(cd), video_device_create_file,
  video_device_remove_file and add the proper checks at create_file
- Converted old norm values to V4L2 ones.
- Robustness on sysfs hue/contrast/saturation queries.
  Additional check in order to return 0 if the driver is not opened.
- Whitespace cleanups in usbvision-cards.c

This patch merges two fixes by Thierry MERLE and Mauro Chehab, and adds
additional checks.

Signed-off-by: Dwaine Garden<DwaineGarden@rogers.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>