viafb: add X server compatibility mode

This patch adds a config option to be compatible with X servers like
OpenChrome. This is required as for example the X server does not
handle things like disabled IGAs/PLLs resulting in a potential
freeze on X startup. With this option disabled we can provide some
nice features like power management and not reinitializing the
hardware on every mode switch (taking long time, causing flickering).

Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 6bafb51b..4923b5e 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -1607,6 +1607,17 @@
 	  correct output device configuration.
 	  Its use is strongly discouraged.
 
+config FB_VIA_X_COMPATIBILITY
+	bool "X server compatibility"
+	depends on FB_VIA
+	default n
+	help
+	  This option reduces the functionality (power saving, ...) of the
+	  framebuffer to avoid negative impact on the OpenChrome X server.
+	  If you use any X server other than fbdev you should enable this
+	  otherwise it should be safe to disable it and allow using all
+	  features.
+
 endif
 
 config FB_NEOMAGIC