gma: Fix loop logic in Scan_Ports()

When deciding if a pipe has been configured, we only checked if reading
the EDID succeeded not if it contained usable data.

TEST=Booted kontron/ktqm77 with a DVI-I to VGA cable and the display
     came up (it didn't before because of a gap in the pipe config, i.e.
     the second pipe was disabled so coreboot didn't bother to look at
     the third).

Change-Id: I10075db8916efcee68be95971145c3f6f1530e5a
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/17087
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/common/hw-gfx-gma.adb b/common/hw-gfx-gma.adb
index cd202be..e6a5928 100644
--- a/common/hw-gfx-gma.adb
+++ b/common/hw-gfx-gma.adb
@@ -334,6 +334,7 @@
                   Configs (Config_Idx).Mode := EDID.Preferred_Mode (Raw_EDID);
                else
                   Configs (Config_Idx).Port := Disabled;
+                  Success := False;
 
                   if Ports (Port_Idx) = Internal and
                      not Port_Configured (Cur_Configs, Internal)