sunxi: H616: Change TF-A load address to beginning of DRAM

Loading Trusted-Firmware's BL31 at 16KB into DRAM was originally a hack
to allow sharing more code with the other SoCs (which use this offset
in SRAM). However there is no longer a reason for that, as the
problematic macros have been properly separated there.

The latest (and hopefully final) TF-A code drop now changes the load
address to the beginning of DRAM, which is also more easily protected
by the Trustzone memory controller (code to be done).

Adjust the load address of BL31 now, to avoid any issues with
incompatible versions later on (the TF-A patches are about to be merged).

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