sunxi: specify architecture when generating SPL boot image

As mkimage -T sunxi_egon now gains support for -A parameter, specify the
architecture when generating SPL boot image for sunxi.

Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl
index 83a95ee..16b5a3d 100644
--- a/scripts/Makefile.spl
+++ b/scripts/Makefile.spl
@@ -411,7 +411,7 @@
 $(obj)/$(SPL_BIN).sfp: $(obj)/$(SPL_BIN).bin FORCE
 	$(call if_changed,mkimage)
 
-MKIMAGEFLAGS_sunxi-spl.bin = -T sunxi_egon \
+MKIMAGEFLAGS_sunxi-spl.bin = -A $(ARCH) -T sunxi_egon \
 	-n $(CONFIG_DEFAULT_DEVICE_TREE)
 
 OBJCOPYFLAGS_u-boot-spl-dtb.hex := -I binary -O ihex --change-address=$(CONFIG_SPL_TEXT_BASE)