[media] v4l: s5p-tv: Fix section mismatch warning in mixer_video.c

[media] v4l: s5p-tv: Fix section mismatch warning in mixer_video.c

The function __devinit mxr_probe() references
a function __devexit mxr_release_video().

Since mxr_release_video() is referenced outside the exit section, the following
compilation warning is generated which is fixed here:

WARNING: drivers/media/video/s5p-tv/s5p-mixer.o(.devinit.text+0x340):
Section mismatch in reference from the function mxr_probe() to the function
devexit.text:mxr_release_video()

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>