Replace custom err() macro with v4l2_err() macro.

[s.nawrocki: added missing end-of-line at the log print]
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>