asus/p2b-d: Transform into variant

TEST=build with BUILD_TIMELESS=1, binary does not change

Change-Id: I1161c726c8c752b5b1e152e1617811989631096e
Signed-off-by: Keith Hui <buurin@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39903
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/asus/p2b/Makefile.inc b/src/mainboard/asus/p2b/Makefile.inc
index 640396e..ca08106 100644
--- a/src/mainboard/asus/p2b/Makefile.inc
+++ b/src/mainboard/asus/p2b/Makefile.inc
@@ -1 +1,2 @@
 ramstage-$(CONFIG_GENERATE_PIRQ_TABLE) += variants/$(VARIANT_DIR)/irq_tables.c
+ramstage-$(CONFIG_GENERATE_MP_TABLE) += variants/$(VARIANT_DIR)/mptable.c