sunxi: simplify U-Boot proper only builds

At the moment every Allwinner board builds and requires an SPL, even
though we select this individually in each _defconfig file.
For experiments and for early bringup of new SoCs it would be beneficial
to only build U-Boot proper, for instance to postpone a tedious SPL port
(including DRAM support) in the initial phase.

Protect some SPL related symbols that we unconditionally select at the
moment with "if SPL", to avoid Kconfig conflicts when CONFIG_SPL is
disabled.

This alone does not cleanly build U-Boot proper only yet, but gets it
far enough so that the binary can be harvested.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index abd7c6c..59e4d4d 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1160,14 +1160,14 @@
 	select SPL_SEPARATE_BSS if SPL
 	select SPL_STACK_R if SPL
 	select SPL_SYS_MALLOC_SIMPLE if SPL
-	select SPL_SYS_THUMB_BUILD if !ARM64
+	select SPL_SYS_THUMB_BUILD if SPL && !ARM64
 	select SUNXI_GPIO
 	select SYS_NS16550
 	select SYS_THUMB_BUILD if !ARM64
 	select USB if DISTRO_DEFAULTS
 	select USB_KEYBOARD if DISTRO_DEFAULTS && USB_HOST
 	select USB_STORAGE if DISTRO_DEFAULTS && USB_HOST
-	select SPL_USE_TINY_PRINTF
+	select SPL_USE_TINY_PRINTF if SPL
 	select USE_PREBOOT
 	select SYS_RELOC_GD_ENV_ADDR
 	imply BOARD_LATE_INIT