Intel and GFXUMA: drop redundant use of lb_add_memory_range()

Use of uma_resource() in northbridge code created a memory
resource marked as reserved. Such resources are removed
from system memory in write_coreboot_table().

Change-Id: I14bfd560140d8d30ec156562f23072bfae747bde
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/1238
Tested-by: build bot (Jenkins)
Reviewed-by: Anton Kochkov <anton.kochkov@gmail.com>

src/mainboard/intel/emeraldlake2/mainboard.c

@@ -44,7 +44,7 @@ void mainboard_suspend_resume(void)
 
 int add_mainboard_resources(struct lb_memory *mem)
 {
-	return add_northbridge_resources(mem);
+	return 0;
 }
 
 #if defined(CONFIG_PCI_OPTION_ROM_RUN_REALMODE) && CONFIG_PCI_OPTION_ROM_RUN_REALMODE