media: zoran: fix sparse warnings

The output is not fully supported yet, so some ops are
commented out. Also comment out the corresponding callbacks to prevent
these sparse warnings:

drivers/staging/media/zoran/zoran_driver.c:656:12: warning: 'zoran_s_output' defined but not used [-Wunused-function]
  656 | static int zoran_s_output(struct file *file, void *__fh, unsigned int output)
      |            ^~~~~~~~~~~~~~
drivers/staging/media/zoran/zoran_driver.c:649:12: warning: 'zoran_g_output' defined but not used [-Wunused-function]
  649 | static int zoran_g_output(struct file *file, void *__fh, unsigned int *output)
      |            ^~~~~~~~~~~~~~
drivers/staging/media/zoran/zoran_driver.c:635:12: warning: 'zoran_enum_output' defined but not used [-Wunused-function]
  635 | static int zoran_enum_output(struct file *file, void *__fh,
      |            ^~~~~~~~~~~~~~~~~
drivers/staging/media/zoran/zoran_driver.c:302:12: warning: 'zoran_enum_fmt_vid_overlay' defined but not used [-Wunused-function]
  302 | static int zoran_enum_fmt_vid_overlay(struct file *file, void *__fh,
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/staging/media/zoran/zoran_driver.c:294:12: warning: 'zoran_enum_fmt_vid_out' defined but not used [-Wunused-function]
  294 | static int zoran_enum_fmt_vid_out(struct file *file, void *__fh,
      |            ^~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>