[PATCH] staging/fbtft: Fix backlight

[Noralf Trønnes]

Den 30.10.2021 18.29, skrev Noralf Trønnes:
> Commit b4a1ed0cd18b ("fbdev: make FB_BACKLIGHT a tristate") forgot to
> update fbtft breaking its backlight support when FB_BACKLIGHT is a module.
> 
> Fix this by using IS_ENABLED().
> 
> Fixes: b4a1ed0cd18b ("fbdev: make FB_BACKLIGHT a tristate")
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
> ---

I discovered that fb_ssd1351 also has this #ifdef, so need to fix that
as well. Will send a new version.

Noralf.