qemuriscv64: Set the Xvisor platform
Set the platform information required to build Xvisor.
https://git.yoctoproject.org/cgit/cgit.cgi/meta-virtualization/tree/recipes-extended/xvisor
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>