drivers/xgi/z9s: Port Linux framebuffer initialization to coreboot

Add native XGI Z9s framebuffer support to coreboot
XGI initialization code largely taken from Linux 3.18.5

TEST: Booted KFSN4-DRE with XGI Volari Z9s into SeaBIOS
with SeaVGABIOS enabled.  Text appeared correctly on screen
and interaction with graphical comboot menu was successful.
However, Linux cleared the framebuffer on boot, rendering the
screen useless until Linux loaded its native xgifb driver.

Change-Id: I606a3892849fc578b0c4d74536aec0a0adef3be3
Signed-off-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
Reviewed-on: http://review.coreboot.org/8331
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/device/Kconfig

@@ -25,6 +25,12 @@ config MAINBOARD_HAS_NATIVE_VGA_INIT
 	bool
 	default n
 
+# FIXME Ugly hack to allow Z9s driver native framebuffer configuration
+config NATIVE_VGA_INIT_USE_EDID
+	bool
+	default n if DRIVERS_XGI_Z9S
+	default y if !DRIVERS_XGI_Z9S
+
 config MAINBOARD_HAS_NATIVE_VGA_INIT_TEXTMODECFG
 	bool
 	default n