soc/apollolake: Add skeleton ACPI entry

Change-Id: Ib127af5392ca2b349480f5b21fad2186b444d7e6
Signed-off-by: Lance Zhao <lijian.zhao@intel.com>
Reviewed-on: https://review.coreboot.org/13348
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/apollolake/Makefile.inc

@@ -25,6 +25,8 @@ romstage-y += memmap.c
 romstage-y += mmap_boot.c
 
 smm-y += placeholders.c
+
+ramstage-$(CONFIG_HAVE_ACPI_TABLES) += acpi.c
 ramstage-y += cpu.c
 ramstage-y += chip.c
 ramstage-y += placeholders.c