RISC-V: KVM: Remove unnecessary 'ret' assignment

RISC-V: KVM: Remove unnecessary 'ret' assignment

If execution reaches "ret = 0" assignment in
kvm_riscv_vcpu_pmu_event_info() then it means
kvm_vcpu_write_guest() returned 0 hence ret is
already zero and does not need to be assigned 0.

Fixes: e309fd113b9f ("RISC-V: KVM: Implement get event info function")
Signed-off-by: Qiang Ma <maqianga@uniontech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251229072530.3075496-1-maqianga@uniontech.com
Signed-off-by: Anup Patel <anup@brainfault.org>