riscv: ae350: support OpenSBI 1.0+ which enable FW_PIC

Original OpenSBI (without FW_PIC) will relocate itself
from 0x1000000 to 0x0. After OpenSBI added FW_PIC codes,
it will not relocate any more and always run at 0x1000000.
Hence, it may overlap with Kernel memory region. So it is
necessary to change OpenSBI address from 0x1000000 to 0x0.

More details can refer to commit cb052d77
("riscv: qemu: spl: Fix booting Linux kernel with OpenSBI 1.0+")

Signed-off-by: Rick Chen <rick@andestech.com>
Reviewed-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Bin Meng <bmeng@tinylab.org>