aopen/dxplplusu: Support SMM_ASEG and SMM_TSEG

Both SMM_ASEG and SMM_TSEG choices work.

There is periodic TCO timeout occurring.
At least with DEBUG_SMI kernel reports low memory corruption.

Change-Id: If20a7092117612a1a9e25eb6ac480e105acd57d7
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61517
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
index be17cf9..5db4537 100644
--- a/src/southbridge/intel/i82801dx/Makefile.inc
+++ b/src/southbridge/intel/i82801dx/Makefile.inc
@@ -15,4 +15,6 @@
 ramstage-y += usb.c
 ramstage-y += usb2.c
 
+smm-y += smihandler.c
+
 endif