atmel_lcdfb: implement inverted contrast pwm

This patch introduces lcdc->lcdcon_pol_negative which set CONTRAST_CTR
 register to inverted polarity.

Signed-off-by: Andreas Bießmann <biessmann@corscience.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/include/video/atmel_lcdc.h b/include/video/atmel_lcdc.h
index 0c864db..28447f1 100644
--- a/include/video/atmel_lcdc.h
+++ b/include/video/atmel_lcdc.h
@@ -52,6 +52,7 @@
 	u8			bl_power;
 #endif
 	bool			lcdcon_is_backlight;
+	bool			lcdcon_pol_negative;
 	u8			saved_lcdcon;
 
 	u8			default_bpp;