[media] drivers: media: i2c: constify v4l2_subdev_* structures

[media] drivers: media: i2c: constify v4l2_subdev_* structures

v4l2_subdev_{core/pad/video}_ops structures are stored in the
fields of the v4l2_subdev_ops structure which are of type const.
Also, v4l2_subdev_ops structure is passed to a function
having its argument of type const. As these structures are never
modified, so declare them as const.
Done using Coccinelle: (One of the scripts used)

@r1 disable optional_qualifier @
identifier i;
position p;
@@
static struct v4l2_subdev_video_ops i@p = {...};

@ok1@
identifier r1.i;
position p;
struct v4l2_subdev_ops obj;
@@
obj.video=&i@p;

@bad@
position p!={r1.p,ok1.p};
identifier r1.i;
@@
i@p

@depends on !bad disable optional_qualifier@
identifier r1.i;
@@
+const
struct v4l2_subdev_video_ops i;

File sizes before:
  text	   data	    bss	    dec	    hex	filename
   7810	    736	     16	   8562	   2172	drivers/media/i2c/mt9p031.o
   9652	    736	     24	  10412	   28ac	drivers/media/i2c/mt9v032.o
   4613	    552	     20	   5185	   1441	drivers/media/i2c/noon010pc30.o
   2615	    552	      8	   3175	    c67	drivers/media/i2c/s5k6a3.o

File sizes after:
  text	   data	    bss	    dec	    hex	filename
   8322	    232	     16	   8570	   217a	drivers/media/i2c/mt9p031.o
  10164	    232	     24	  10420	   28b4	drivers/media/i2c/mt9v032.o
   4933	    232	     20	   5185	   1441	drivers/media/i2c/noon010pc30.o
   2935	    232	      8	   3175	    c67	drivers/media/i2c/s5k6a3.o

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>