riscv: KVM: Switch has_svinval() to riscv_has_extension_unlikely()

Switch has_svinval() from static branch to the new helper
riscv_has_extension_unlikely().

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Acked-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20230128172856.3814-13-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>