sunxi: spl: Disable padding from SPL_PAD_TO

sunxi: spl: Disable padding from SPL_PAD_TO

Starting with H6, Allwinner removed the artificial 32 KiB SPL size limit
from the boot ROM. Now SPL size is only limited by the available SRAM.
This limit ranges from 152 KiB on H6 to a whopping 2052 KiB on R329. To
take advantage of this additional space, we must increase SPL_MAX_SIZE.
Since we do not want to unnecessarily pad SPL out to these giant sizes,
we must set SPL_PAD_TO to zero. This causes no problems because binman
already takes care of appending the SPL payload at the right offset.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>