fbdev: i810: make fb_ops const

Make the structure const as it is only used during a copy operation.
Done using Coccinelle.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>