sunxi: video: Make pwm polarity configurable

It turns out that there are some panels where the pwm input is not active low,
so make it configurable.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/board/sunxi/Kconfig b/board/sunxi/Kconfig
index 0e3c207..738b55e 100644
--- a/board/sunxi/Kconfig
+++ b/board/sunxi/Kconfig
@@ -319,6 +319,13 @@
 	Set the backlight pwm pin for the LCD panel. This takes a string in the
 	format understood by sunxi_name_to_gpio, e.g. PH1 for pin 1 of port H.
 
+config VIDEO_LCD_BL_PWM_ACTIVE_LOW
+	bool "LCD panel backlight pwm is inverted"
+	depends on VIDEO
+	default y
+	---help---
+	Set this if the backlight pwm output is active low.
+
 
 # Note only one of these may be selected at a time! But hidden choices are
 # not supported by Kconfig