[PATCH] DVB: Fix locking to prevent Oops on SMP systems

Fix locking to prevent Oops on SMP systems when starting/stopping dvb network
interfaces.

Signed-off-by: Ralph Metzler <rjkm@metzlerbros.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>