platform/x86: fujitsu-laptop: sync brightness in set_lcd_level()

When using brightness keys and backlight device's sysfs interface
alternately, an incorrect input event might be generated for a
brightness key press.  Consider the following sequence of events:

 1. Set backlight brightness to 6 using brightness keys.
 2. Write 4 to /sys/class/backlight/fujitsu-laptop/brightness.
 3. Press the "brightness up" key.

The input event generated in this scenario would be KEY_BRIGHTNESSDOWN,
because before step 3 brightness_level would still be at 6.  As the new
brightness level is established using GBLL, it would evaluate to 5
(SBLL/SBL2 sets it to 4 in step 2 and pressing the "brightness up" key
increases it by 1).  This in turn would cause acpi_fujitsu_bl_notify()
to observe a 6 -> 5 change, i.e. a decrease in brightness, while screen
brightness would in fact be increased.

Fix this by updating brightness_level in set_lcd_level.

Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Reviewed-by: Jonathan Woithe <jwoithe@just42.net>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/platform/x86/fujitsu-laptop.c

@@ -369,6 +369,8 @@ static int set_lcd_level(int level)
 		return -ENODEV;
 	}
 
+	fujitsu_bl->brightness_level = level;
+
 	return 0;
 }