sunxi: Convert 64-bit boards to use binman

At present 64-bit sunxi boards use the Makefile to create a FIT, using
USE_SPL_FIT_GENERATOR. This is deprecated.

Update sunxi to use binman instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/Kconfig b/Kconfig
index 883e3f7..837b2f5 100644
--- a/Kconfig
+++ b/Kconfig
@@ -659,12 +659,11 @@
 
 config USE_SPL_FIT_GENERATOR
 	bool "Use a script to generate the .its script"
-	default y if SPL_FIT
+	default y if SPL_FIT && !ARCH_SUNXI
 
 config SPL_FIT_GENERATOR
 	string ".its file generator script for U-Boot FIT image"
 	depends on USE_SPL_FIT_GENERATOR
-	default "board/sunxi/mksunxi_fit_atf.sh" if SPL_LOAD_FIT && ARCH_SUNXI
 	default "arch/arm/mach-rockchip/make_fit_atf.py" if SPL_LOAD_FIT && ARCH_ROCKCHIP
 	default "arch/arm/mach-zynqmp/mkimage_fit_atf.sh" if SPL_LOAD_FIT && ARCH_ZYNQMP
 	default "arch/riscv/lib/mkimage_fit_opensbi.sh" if SPL_LOAD_FIT && RISCV