x86: Add SPL build rules for start-up code

When SPL is used we need to build the 16-bit start-up code. Add Makefile
rules to handle this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

scripts/Makefile.spl

@@ -179,6 +179,8 @@ ifeq ($(CONFIG_SYS_SOC),"at91")
 ALL-y	+= boot.bin
 endif
 
+ALL-$(CONFIG_SPL_X86_16BIT_INIT) += $(obj)/u-boot-x86-16bit-spl.bin
+
 ALL-$(CONFIG_ARCH_ZYNQ)		+= $(obj)/boot.bin
 ALL-$(CONFIG_ARCH_ZYNQMP)	+= $(obj)/boot.bin
 
@@ -263,11 +265,16 @@ endif
 quiet_cmd_objcopy = OBJCOPY $@
 cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@
 
-OBJCOPYFLAGS_$(SPL_BIN)-nodtb.bin = $(SPL_OBJCFLAGS) -O binary
+OBJCOPYFLAGS_$(SPL_BIN)-nodtb.bin = $(SPL_OBJCFLAGS) -O binary \
+		$(if $(CONFIG_SPL_X86_16BIT_INIT),-R .start16 -R .resetvec)
 
 $(obj)/$(SPL_BIN)-nodtb.bin: $(obj)/$(SPL_BIN) FORCE
 	$(call if_changed,objcopy)
 
+OBJCOPYFLAGS_u-boot-x86-16bit-spl.bin := -O binary -j .start16 -j .resetvec
+$(obj)/u-boot-x86-16bit-spl.bin: $(obj)/u-boot-spl FORCE
+	$(call if_changed,objcopy)
+
 LDFLAGS_$(SPL_BIN) += -T u-boot-spl.lds $(LDFLAGS_FINAL)
 ifneq ($(CONFIG_SPL_TEXT_BASE),)
 LDFLAGS_$(SPL_BIN) += -Ttext $(CONFIG_SPL_TEXT_BASE)