v3d/simulator: size counter_values array correctly on V3D 7.x

Fixes incorrect sizing of counter_values array in the simulator path.

sim_state.perfcnt_total provides the total number of counters supported by the underlying simulated platform and is what we use when we create a perform to validate that the counters requested are valid, so we should use this.

V3D_PERFCNT_NUM is a fixed enum value that is only valid for V3D 4.2 at present and is not sufficiently large for all the counters available in V3D 7.x.