target/riscv/kvm: add kvm_riscv_reset_regs_csr()

target/riscv/kvm: add kvm_riscv_reset_regs_csr()

We're setting reset vals for KVM csrs during kvm_riscv_reset_vcpu(), but
in no particular order and missing some of them (like env->mstatus).

Create a helper to do that, unclogging reset_vcpu(), and initialize
env->mstatus as well. Keep the regs in the same order they appear in
struct kvm_riscv_csr from the KVM UAPI, similar to what
kvm_riscv_(get|put)_regs_csr are doing. This will make a bit easier to
add new KVM CSRs and to verify which values we're writing back to KVM
during vcpu reset.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250224123120.1644186-3-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>