V4L/DVB (6152): cx23885: forward compatibility fixes for recent kernels

- fix #include for <media/video-buf-dvb.h>
- fix cx23885_irq declaration for 2.6.19 and later

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>