sunxi: Use mkimage for SPL boot image generation

Switch the SPL boot image generation from using mksunxiboot to the new
sunxi_egon format of mkimage.

Verified to create identical results for all 152 Allwinner boards.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net>
Reviewed-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Samuel Holland <samuel@sholland.org>
diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl
index 87021e2..ea4e045 100644
--- a/scripts/Makefile.spl
+++ b/scripts/Makefile.spl
@@ -386,11 +386,11 @@
 $(obj)/$(SPL_BIN).sfp: $(obj)/$(SPL_BIN).bin FORCE
 	$(call if_changed,mkimage)
 
-quiet_cmd_mksunxiboot = MKSUNXI $@
-cmd_mksunxiboot = $(objtree)/tools/mksunxiboot \
-			--default-dt $(CONFIG_DEFAULT_DEVICE_TREE) $< $@
+MKIMAGEFLAGS_sunxi-spl.bin = -T sunxi_egon \
+	-n $(CONFIG_DEFAULT_DEVICE_TREE)
+
 $(obj)/sunxi-spl.bin: $(obj)/$(SPL_BIN).bin FORCE
-	$(call if_changed,mksunxiboot)
+	$(call if_changed,mkimage)
 
 quiet_cmd_sunxi_spl_image_builder = SUNXI_SPL_IMAGE_BUILDER $@
 cmd_sunxi_spl_image_builder = $(objtree)/tools/sunxi-spl-image-builder \