sunxi: Enable CONFIG_SPL_STACK_R

Select CONFIG_SPL_STACK_R for sunxi boards, this gives us much more
room on the stack once we've the DRAM running.

Besides being a good change to have on itself, this also paves the
way for switching to using malloc_simple in the SPL which cuts of
close to 4KiB of the SPL size.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 7981355..1a7e916 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -522,6 +522,7 @@
 	select DM_USB
 	select OF_CONTROL
 	select OF_SEPARATE
+	select SPL_STACK_R if !MACH_SUN9I
 	select USB
 	select USB_STORAGE
 	select USB_KEYBOARD