sb/amd/cimx/sb800: add C bootblock southbridge initialization

TEST=boot PC Engines apu1 with C bootblock patch and launch
Debian with Linux kernel 4.14.50

Signed-off-by: Michał Żygowski <michal.zygowski@3mdeb.com>
Change-Id: Ie81198f5034a84d319ee7143aa032433f82be254
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37329
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/southbridge/amd/cimx/sb800/Makefile.inc b/src/southbridge/amd/cimx/sb800/Makefile.inc
index 418110b..ccb3a2a 100644
--- a/src/southbridge/amd/cimx/sb800/Makefile.inc
+++ b/src/southbridge/amd/cimx/sb800/Makefile.inc
@@ -16,6 +16,10 @@
 
 # SB800 Platform Files
 
+ifneq ($(CONFIG_ROMCC_BOOTBLOCK),y)
+bootblock-y += bootblock.c
+endif
+
 romstage-y += cfg.c
 romstage-y += early.c
 romstage-y += smbus.c smbus_spd.c