Makefile: Align BITBANG_SPI with the other DEPENDS_ and USE_ configs

Drop not needed `-DCONFIG_BITBANG_SPI=1`

Change-Id: I2a519c929f7747af70568284823b51678751e285
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/63886
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72327
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/Makefile b/Makefile
index 1140b8c..631a192 100644
--- a/Makefile
+++ b/Makefile
@@ -534,14 +534,6 @@
 		$(eval $(var)=yes)))
 endif
 
-# Bitbanging SPI infrastructure, default off unless needed.
-
-ifneq ($(call filter_deps,$(DEPENDS_ON_BITBANG_SPI)), )
-override CONFIG_BITBANG_SPI = yes
-else
-CONFIG_BITBANG_SPI ?= no
-endif
-
 ###############################################################################
 # Handle CONFIG_* variables that depend on others set (and verified) above.
 
@@ -606,11 +598,6 @@
 PROGRAMMER_OBJS += pony_spi.o
 endif
 
-ifeq ($(CONFIG_BITBANG_SPI), yes)
-FEATURE_FLAGS += -D'CONFIG_BITBANG_SPI=1'
-PROGRAMMER_OBJS += bitbang_spi.o
-endif
-
 ifeq ($(CONFIG_NIC3COM), yes)
 FEATURE_FLAGS += -D'CONFIG_NIC3COM=1'
 PROGRAMMER_OBJS += nic3com.o
@@ -766,6 +753,11 @@
 PROGRAMMER_OBJS += ni845x_spi.o
 endif
 
+USE_BITBANG_SPI := $(if $(call filter_deps,$(DEPENDS_ON_BITBANG_SPI)),yes,no)
+ifeq ($(USE_BITBANG_SPI), yes)
+LIB_OBJS += bitbang_spi.o
+endif
+
 USE_SERIAL := $(if $(call filter_deps,$(DEPENDS_ON_SERIAL)),yes,no)
 ifeq ($(USE_SERIAL), yes)
 LIB_OBJS += serial.o