Revert "mb/aopen/dxplplusu: Remove board"

This reverts commit eb76a455cd39ec59b7f2ba28baeec9538befd59e
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>
diff --git a/src/southbridge/intel/i82801dx/Makefile.inc b/src/southbridge/intel/i82801dx/Makefile.inc
new file mode 100644
index 0000000..c352e3e
--- /dev/null
+++ b/src/southbridge/intel/i82801dx/Makefile.inc
@@ -0,0 +1,17 @@
+## SPDX-License-Identifier: GPL-2.0-only
+
+ifeq ($(CONFIG_SOUTHBRIDGE_INTEL_I82801DX),y)
+
+ramstage-y += i82801dx.c
+ramstage-y += ac97.c
+ramstage-y += fadt.c
+ramstage-y += ide.c
+ramstage-y += lpc.c
+ramstage-y += usb.c
+ramstage-y += usb2.c
+
+romstage-y += early_smbus.c
+
+bootblock-y += bootblock.c
+
+endif