amdfwtool: Clean up the Makefile of amdfwtool

Add Makefile.inc to compliant with other tools.
Makefile is kept for building amdfwtool by typing make
in the folder.

Change-Id: I3688d93de4459f5f838955892086b4b9bf30a9b8
Signed-off-by: Zheng Bao <fishbaozi@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45286
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
diff --git a/Makefile.inc b/Makefile.inc
index a43de5e..bf33f8b 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -81,7 +81,7 @@
 subdirs-y += src/superio
 subdirs-y += $(wildcard src/drivers/*) $(wildcard src/drivers/*/*)
 subdirs-y += src/cpu src/vendorcode
-subdirs-y += util/cbfstool util/sconfig util/nvramtool util/pgtblgen
+subdirs-y += util/cbfstool util/sconfig util/nvramtool util/pgtblgen util/amdfwtool
 subdirs-y += util/futility util/marvell util/bincfg util/supermicro
 subdirs-y += $(wildcard src/arch/*)
 subdirs-y += src/mainboard/$(MAINBOARDDIR)
@@ -576,9 +576,6 @@
 	cp -a $(top)/util/ifdtool/ifdtool $@
 
 AMDFWTOOL:=$(objutil)/amdfwtool/amdfwtool
-$(AMDFWTOOL): $(top)/util/amdfwtool/amdfwtool.c
-	@printf "    HOSTCC     $(subst $(obj)/,,$(@))\n"
-	$(HOSTCC) $(HOSTCFLAGS) -DCONFIG_ROM_SIZE=$(CONFIG_ROM_SIZE) -o $@ $<
 
 APCB_EDIT_TOOL:=$(top)/util/apcb/apcb_edit.py
 
@@ -1108,7 +1105,6 @@
 endif
 
 $(obj)/coreboot.rom: $(obj)/coreboot.pre $(RAMSTAGE) $(CBFSTOOL) $$(INTERMEDIATE)
-
 	@printf "    CBFS       $(subst $(obj)/,,$(@))\n"
 # The full ROM may be larger than the CBFS part, so create an empty
 # file (filled with \377 = 0xff) and copy the CBFS image over it.