video: fbdev: make fb_videomode const

Make these const as they are only passed to a const argument of the
function fb_find_mode.

Done using Coccinelle.

@match disable optional_qualifier@
identifier s;
@@
static struct fb_videomode s = {...};

@ref@
position p;
identifier match.s;
@@
s@p

@good1@
identifier match.s;
expression list[5] es;
position ref.p;
@@
fb_find_mode(es,&s@p,...)

@bad depends on  !good1@
position ref.p;
identifier match.s;
@@
s@p

@depends on forall !bad disable optional_qualifier@
identifier match.s;
@@
static
+ const
struct fb_videomode s;

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>