target/riscv/cpu.c: split kvm prop handling to its own helper

target/riscv/cpu.c: split kvm prop handling to its own helper

Future patches will split the existing Property arrays even further, and
the existing code in riscv_cpu_add_user_properties() will start to scale
bad with it because it's dealing with KVM constraints mixed in with TCG
constraints. We're going to pay a high price to share a couple of common
lines of code between the two.

Create a new kvm_riscv_cpu_add_kvm_properties() helper that will be
forked from riscv_cpu_add_user_properties() if we're running KVM. The
helper includes all properties that a KVM CPU will add. The rest of
riscv_cpu_add_user_properties() body will then be relieved from having
to deal with KVM constraints.

The helper was declared in kvm_stubs.h, while being implemented in
cpu.c, to allow '--enable-debug' builds to work. The compiler won't
remove the kvm_riscv_cpu_add_kvm_properties() reference when
'kvm_enabled()' is false if we end up with an unused function. Even
though being a KVM only helper we can't implement it in kvm.c due to its
many dependencies inside cpu.c, so make it public in kvm_riscv.h and
keep its implementation in cpu.c for now. We'll move it to kvm.c in the
near future.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Message-ID: <20230912132423.268494-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>