video: fbdev: controlfb: fix sparse warning about using incorrect type

Use in_le32() instead of le32_to_cpup() to fix sparse warning about
improper type of the argument.

Also drop inline keyword from control_par_to_var() prototype
(to match function definition).

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200324134508.25120-2-b.zolnierkie@samsung.com