[media] exynos4-is: 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_ops i@p = {...};

@ok1@
identifier r1.i;
position p;
expression e1;
@@
v4l2_subdev_init(e1,&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_ops i;

File size before:
   text	   data	    bss	    dec	    hex	filename
  16830	   1064	      0	  17894	   45e6 platform/exynos4-is/fimc-capture.o
   7787	    704	     20	   8511	   213f platform/exynos4-is/mipi-csis.o

File size after:
   text	   data	    bss	    dec	    hex	filename
  17022	    880	      0	  17902	   45ee platform/exynos4-is/fimc-capture.o
   8299	    192	     20	   8511	   213f platform/exynos4-is/mipi-csis.o

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>