The current riscv_load_fdt() forces fdt_load_addr to be placed at a dram address within 3GB,
but not all platforms have dram_base within 3GB.

This patch adds an exception for dram base not within 3GB,
which will place fdt at dram_end align 16MB.

riscv_setup_rom_reset_vec() also needs to be modified

Signed-off-by: Dylan Jhong <dylan@andestech.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220419115945.37945-1-dylan@andestech.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>