ARM: sunxi: Build u-boot-sunxi-with-spl.bin on ARM64 as well

In README.sunxi64 we tell the user how to optionally create
u-boot-sunxi-with-spl.bin by manually running cat. Instead, have the
build system create the file automatically just like it does for 32-bit
sunxi boards.

Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>

Makefile

@@ -1191,8 +1191,13 @@ u-boot-x86-16bit.bin: u-boot FORCE
 endif
 
 ifneq ($(CONFIG_ARCH_SUNXI),)
+ifeq ($(CONFIG_ARM64),)
 u-boot-sunxi-with-spl.bin: spl/sunxi-spl.bin u-boot.img u-boot.dtb FORCE
 	$(call if_changed,binman)
+else
+u-boot-sunxi-with-spl.bin: spl/sunxi-spl.bin u-boot.itb FORCE
+	$(call if_changed,cat)
+endif
 endif
 
 ifneq ($(CONFIG_TEGRA),)

board/sunxi/README.sunxi64

@@ -95,9 +95,8 @@ Transfer the SPL and the U-Boot FIT image directly to an uSD card:
 (replace /dev/sdx with you SD card device file name, which could be
 /dev/mmcblk[x] as well).
 
-Alternatively you can concatenate the SPL and the U-Boot FIT image into a
+Alternatively you can use the SPL and the U-Boot FIT image combined into a
 single file and transfer that instead:
-$ cat spl/sunxi-spl.bin u-boot.itb > u-boot-sunxi-with-spl.bin
 # dd if=u-boot-sunxi-with-spl.bin of=/dev/sdx bs=8k seek=1
 
 You can partition the microSD card, but leave the first MB unallocated (most