V4L/DVB (5110): Keep the previous tvnorm default for cx88 and cx88-blackbird

The video_ioctl2 conversion replaced the default from NTSC to PAL_BG.
This broke cx88-blackbird. Probably, there are some badness at this
driver, not doing all required stuff to change video standard.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>