riscv: create a loader.bin boot image for Kendryte SoC

Create the loader.bin bootable image file that can be loaded into
Kendryte K210 based boards using the kflash.py tool with the command:

kflash.py/kflash.py -t arch/riscv/boot/loader.bin
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/Makefile

@@ -83,12 +83,12 @@ PHONY += vdso_install
 vdso_install:
 	$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
 
-ifeq ($(CONFIG_RISCV_M_MODE),y)
-KBUILD_IMAGE := $(boot)/loader
+ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_KENDRYTE),yy)
+KBUILD_IMAGE := $(boot)/loader.bin
 else
 KBUILD_IMAGE := $(boot)/Image.gz
 endif
-BOOT_TARGETS := Image Image.gz loader
+BOOT_TARGETS := Image Image.gz loader loader.bin
 
 all:	$(notdir $(KBUILD_IMAGE))
 

arch/riscv/boot/Makefile

@@ -41,6 +41,9 @@ $(obj)/Image.lzma: $(obj)/Image FORCE
 $(obj)/Image.lzo: $(obj)/Image FORCE
 	$(call if_changed,lzo)
 
+$(obj)/loader.bin: $(obj)/loader FORCE
+	$(call if_changed,objcopy)
+
 install:
 	$(CONFIG_SHELL) $(srctree)/$(src)/install.sh $(KERNELRELEASE) \
 	$(obj)/Image System.map "$(INSTALL_PATH)"