V4L/DVB (7378): cleanup variable initialization

flags used for spinlocks don't need to be initialized, except where the
compiler has no way to see, that the spin_unlock_irqrestore is only called
if the spin_lock_irqsave has been called before. Local variable
initialization doesn't have to be protected.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de>
Reviewed-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>