[media] media: au0828 set ctrl_input in au0828_s_input()

dev->ctrl_input is set in vidioc_s_input() and doesn't get set in
au0828_s_input(). As a result, dev->ctrl_input is left uninitialized
until user space calls s_input.

It works correctly because the default input value is 0 and which is
what dev->ctrl_input gets initialized via kzalloc().

Change to set dev->ctrl_input in au0828_s_input(). Also optimize
vidioc_s_input() to return if the new input value is same as the
current.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>