[media] exynos4-is: Disable debug trace by default in fimc-isp.c

Make sure the debug level is properly set initially so any debug
information is not printed to the kernel log without explicitly
enabling it.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>