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/mainboard/aopen/dxplplusu/Kconfig b/src/mainboard/aopen/dxplplusu/Kconfig
new file mode 100644
index 0000000..5c0ca2b
--- /dev/null
+++ b/src/mainboard/aopen/dxplplusu/Kconfig
@@ -0,0 +1,27 @@
+if BOARD_AOPEN_DXPLPLUSU
+
+config BOARD_SPECIFIC_OPTIONS
+	def_bool y
+	select CPU_INTEL_SOCKET_MPGA604
+	select NORTHBRIDGE_INTEL_E7505
+	select SOUTHBRIDGE_INTEL_I82870
+	select SOUTHBRIDGE_INTEL_I82801DX
+	select SUPERIO_SMSC_LPC47M10X
+	select HAVE_ACPI_TABLES
+	select BOARD_ROMSIZE_KB_2048
+
+config MAINBOARD_DIR
+	default "aopen/dxplplusu"
+
+config MAINBOARD_PART_NUMBER
+	default "DXPL Plus-U"
+
+config IRQ_SLOT_COUNT
+	int
+	default 12
+
+config MAX_CPUS
+	int
+	default 4
+
+endif # BOARD_AOPEN_DXPLPLUSU