media: bt819: Reduce amount of F* words in the world

Replace F* word with something less offensive.

[hverkuil: dropped 'Fixes: 1da177e4 ("Linux-2.6.12-rc2")' tag since nothing was broken]

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>