gma config_helpers: Pass only the modeline to Validate_Config()

Validate_Config() had the full `Port_Config` as parameter, though we
only accessed the modeline. Make that explicit so we can also call it
when we don't have the full config available.

Change-Id: Ia4620d1ffa1a3cd098d721d84f2453f2dc19da2a
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/23163
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/common/hw-gfx-gma.adb b/common/hw-gfx-gma.adb
index 0e2c835..4a1264c 100644
--- a/common/hw-gfx-gma.adb
+++ b/common/hw-gfx-gma.adb
@@ -109,7 +109,7 @@
 
       if Success then
          Success := Config_Helpers.Validate_Config
-           (Pipe_Cfg.Framebuffer, Port_Cfg, Pipe);
+           (Pipe_Cfg.Framebuffer, Port_Cfg.Mode, Pipe);
       end if;
 
       if Success then