hw/riscv/riscv-iommu: add IOCOUNTINH mmio writes

hw/riscv/riscv-iommu: add IOCOUNTINH mmio writes

RISCV_IOMMU_REG_IOCOUNTINH is done by riscv_iommu_process_iocntinh_cy(),
which is called during riscv_iommu_mmio_write() callback via a new
riscv_iommu_pricess_hpm_writes() helper.

Signed-off-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250224190826.1858473-7-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>