video: fbdev: controlfb: remove function prototypes part #2

Reorder code a bit and then remove no longer needed function
prototypes.

Acked-by: Sam Ravnborg <[email protected]>
Signed-off-by: Bartlomiej Zolnierkiewicz <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]