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

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

Since the SRAM C corruption issue is now resolved on Allwinner
A64, it is possible to move the stack top to the address 0x1A000
on both A64 and A80. The boot ROM can load SPL binaries with
up to 32 KiB size on A64 (the 24 KiB SPL size limitation only
affects A10/A20), and this patch also ensures the availability
of 8 KiB stack.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>