riscv: qemu: Set kernel_comp_addr_r for compressed kernel

Set kernel_comp_addr_r and kernel_comp_size for compressed kernel.
Adjust existing addresses for ramdisk, so that kernel_comp_addr_r
comes before the ramdisk image, since the decompressed kernel size
is known to us. This way we can allow big ramdisk image to be loaded.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>