backlight/fbcon: Add FB_EVENT_CONBLANK

The backlight class wants notification whenever the console is blanked
but doesn't get this when hardware blanking fails and software blanking
is used. Changing FB_EVENT_BLANK to report both would be a behaviour
change which could confuse the console layer so add a new event for
software blanking and have the backlight class listen for both.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
diff --git a/include/linux/fb.h b/include/linux/fb.h
index a78e256..bf7158b 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -516,13 +516,15 @@
 #define FB_EVENT_GET_CONSOLE_MAP        0x07
 /*      CONSOLE-SPECIFIC: set console to framebuffer mapping */
 #define FB_EVENT_SET_CONSOLE_MAP        0x08
-/*      A display blank is requested       */
+/*      A hardware display blank change occured */
 #define FB_EVENT_BLANK                  0x09
 /*      Private modelist is to be replaced */
 #define FB_EVENT_NEW_MODELIST           0x0A
 /*	The resolution of the passed in fb_info about to change and
         all vc's should be changed         */
 #define FB_EVENT_MODE_CHANGE_ALL	0x0B
+/*	A software display blank change occured */
+#define FB_EVENT_CONBLANK               0x0C
 
 struct fb_event {
 	struct fb_info *info;