hw/riscv: virt: Allow creating multiple NUMA sockets

hw/riscv: virt: Allow creating multiple NUMA sockets

We extend RISC-V virt machine to allow creating a multi-socket
machine. Each RISC-V virt machine socket is a NUMA node having
a set of HARTs, a memory instance, a CLINT instance, and a PLIC
instance. Other devices are shared between all sockets. We also
update the generated device tree accordingly.

By default, NUMA multi-socket support is disabled for RISC-V virt
machine. To enable it, users can use "-numa" command-line options
of QEMU.

Example1: For two NUMA nodes with 2 CPUs each, append following
to command-line options: "-smp 4 -numa node -numa node"

Example2: For two NUMA nodes with 1 and 3 CPUs, append following
to command-line options:
"-smp 4 -numa node -numa node -numa cpu,node-id=0,core-id=0 \
-numa cpu,node-id=1,core-id=1 -numa cpu,node-id=1,core-id=2 \
-numa cpu,node-id=1,core-id=3"

The maximum number of sockets in a RISC-V virt machine is 8
but this limit can be changed in future.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Message-Id: <20200616032229.766089-6-anup.patel@wdc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>