Revert "mb/aopen/dxplplusu: Remove board"

This reverts commit eb76a455cd
and applies minor fixes to make it build again.

PARALLEL_MP was working prior to board removal and no
relevant SMI handlers were implemented. So NO_SMM choice
is now selected.

Change-Id: Ia1cd02278240d1b5d006fb2a7730d3d86390f85b
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69339
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/southbridge/intel/i82870/pcibridge.c

@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <device/device.h>
+#include <device/pci.h>
+#include <device/pci_ids.h>
+#include <device/pci_ops.h>
+#include "82870.h"
+
+static void p64h2_pcix_init(struct device *dev)
+{
+	u32 dword;
+	u8 byte;
+
+	/* The purpose of changes to HCCR, ACNF, and MTT is to speed
+	 * up the PCI bus for cards having high speed transfers.
+	 */
+	dword = 0xc2040002;
+	pci_write_config32(dev, HCCR, dword);
+	dword = 0x0000c3bf;
+	pci_write_config32(dev, ACNF, dword);
+	byte = 0x08;
+	pci_write_config8(dev, MTT, byte);
+
+}
+static struct device_operations pcix_ops  = {
+	.read_resources   = pci_bus_read_resources,
+	.set_resources    = pci_dev_set_resources,
+	.enable_resources = pci_bus_enable_resources,
+	.init             = p64h2_pcix_init,
+	.scan_bus         = pci_scan_bridge,
+	.reset_bus        = pci_bus_reset,
+};
+
+static const struct pci_driver pcix_driver __pci_driver = {
+	.ops    = &pcix_ops,
+	.vendor = PCI_VID_INTEL,
+	.device = PCI_DID_INTEL_82870_1F0,
+};
+
+struct chip_operations southbridge_intel_i82870_ops = {
+	CHIP_NAME("Intel 82870")
+};