RISC-V: KVM: Fix to allow hpmcounter31 from the guest

RISC-V: KVM: Fix to allow hpmcounter31 from the guest

The csr_fun defines a count parameter which defines the total number
CSRs emulated in KVM starting from the base. This value should be
equal to total number of counters possible for trap/emulation (32).

Fixes: a9ac6c37521f ("RISC-V: KVM: Implement trap & emulate for hpmcounters")
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20240816-kvm_pmu_fixes-v1-2-cdfce386dd93@rivosinc.com
Signed-off-by: Anup Patel <anup@brainfault.org>