V4L/DVB (8317): Sensoray 2255 V4l driver checkpatch fixes

This patch fixes some coding style issues.
It also fixes a NULL de-reference on driver unload.
The permissions for the module parameters were changed to 0644.

Signed-off-by: Dean Anderson <dean@sensoray.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>