soc/intel/skylake: Generate ACPI DMAR table

If the SoC is VT-d capable, write an ACPI DMAR table. The entry for the
GFXVTBAR is only generated if the IGD is enabled.

Change-Id: I8176401dd19aee7ad09a8a145b7a3801fe5b2ae1
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/21588
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Youness Alaoui <snifikino@gmail.com>

src/soc/intel/skylake/chip_fsp20.c

@@ -60,7 +60,8 @@ static struct device_operations pci_domain_ops = {
 	.scan_bus         = &pci_domain_scan_bus,
 	.ops_pci_bus      = &pci_bus_default_ops,
 #if IS_ENABLED(CONFIG_HAVE_ACPI_TABLES)
-	.acpi_name        = &soc_acpi_name,
+	.write_acpi_tables	= &northbridge_write_acpi_tables,
+	.acpi_name		= &soc_acpi_name,
 #endif
 };