target/riscv: Fix PMU CSR predicate function

target/riscv: Fix PMU CSR predicate function

The predicate function calculates the counter index incorrectly for
hpmcounterx. Fix the counter index to reflect correct CSR number.

Fixes: e39a8320b088 ("target/riscv: Support the Virtual Instruction fault")
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Message-Id: <20220620231603.2547260-2-atishp@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>