SeaVGABios/cbvga: Use active mode to clear screen

As coreboot framebuffer is immutable always use CBmodeinfo.

Signed-off-by: Patrick Rudolph <siro@das-labor.org>
diff --git a/vgasrc/cbvga.c b/vgasrc/cbvga.c
index 417ade3..4b7cd0e 100644
--- a/vgasrc/cbvga.c
+++ b/vgasrc/cbvga.c
@@ -105,7 +105,7 @@
             return 0;
         }
         struct gfx_op op;
-        init_gfx_op(&op, vmode_g);
+        init_gfx_op(&op, &CBmodeinfo);
         op.x = op.y = 0;
         op.xlen = GET_GLOBAL(CBmodeinfo.width);
         op.ylen = GET_GLOBAL(CBmodeinfo.height);