[PATCH] fbdev: include backlight.h only when __KERNEL__ is defined

linux/backlight.h pulls in header files (eg.  ioport.h) that break
compilation of userspace programs.  To solve the problem, only include
backlight.h in fb.h if compiling kernel stuff.

Signed-off-by: Michal Januszewski <spock@gentoo.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>