hw/loader: Pass ELFDATA endian order argument to load_elf_ram_sym()

Rather than passing a boolean 'is_big_endian' argument,
directly pass the ELFDATA, which can be unspecified using
the ELFDATANONE value.

Update the call sites:
  0 -> ELFDATA2LSB

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20250127113824.50177-5-philmd@linaro.org>