hw/riscv: spike: Decouple create_fdt() dependency to ELF loading

hw/riscv: spike: Decouple create_fdt() dependency to ELF loading

At present create_fdt() calls htif_uses_elf_symbols() to determine
whether to insert a <reg> property for the HTIF. This unfortunately
creates a hidden dependency to riscv_load_{firmware,kernel} that
create_fdt() must be called after the ELF {firmware,kernel} image
has been loaded.

Decouple such dependency be adding a new parameter to create_fdt(),
whether custom HTIF base address is used. The flag will be set if
non ELF {firmware,kernel} image is given by user.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-Id: <20221229091828.1945072-13-bmeng@tinylab.org>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>