V4L/DVB (6215): Bugfix for saa6588.c, add forgotten spin_lock_init()

There's a serious bug in saa6588.c, it uses a non-initialized spin_lock.
Funny thing is that it works fine with bttv, but completly freezes the
machine if e.g. saa7134 is loaded.

Thanks to Derek Philip for reporting this bug on the rdsd-devel list.

This patch adds the missing spin_lock_init().

Signed-off-by: Hans J. Koch <hjk@linutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>