hw/riscv/riscv-iommu-bits.h: HPM bits

hw/riscv/riscv-iommu-bits.h: HPM bits

Add the relevant HPM (High Performance Monitor) bits that we'll be using
in the next patches.

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: <20250224190826.1858473-3-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>