media: stb0899_algo: initialize cfr before using it

The loop at stb0899_search_carrier() starts with a random
value for cfr, as reported by Coverity.

Initialize it to zero, just like stb0899_dvbs_algo() to ensure
that carrier search won't bail out.

Fixes: 8bd135ba ("V4L/DVB (9375): Add STB0899 support")
Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>