Revert "sunxi: Move the SPL stack top to 0x1A000 on Allwinner A64/A80"

Revert "sunxi: Move the SPL stack top to 0x1A000 on Allwinner A64/A80"

This commit moved the SPL stack into SRAM C, which worked when the SPL
set the AHB1 clock down to 100 MHz to cope with the flaky SRAM C access
from the CPU.
However booting with boot0 (and thus not using SPL at all) we still run
with a 200 MHz AHB1, so any access to SRAM C is prone to fail.
Since this commit does _not_ only affect the SPL code, but also the
U-Boot proper, we fail when booting with boot0.

As the introduction of tiny-printf reduced the size of the SPL, we
can afford to have the SPL stack in SRAM A1.

This reverts commit 1a83fb4a17d959d7b037999ab7ed7e62429abe34
and fixes booting the Pine64 when using boot0.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>