hw/riscv/riscv-iommu.c: Introduce a translation tag for the page table cache

hw/riscv/riscv-iommu.c: Introduce a translation tag for the page table cache

This commit introduces a translation tag to avoid invalidating an entry
that should not be invalidated when IOMMU executes invalidation commands.
E.g. IOTINVAL.VMA with GV=0, AV=0, PSCV=1 invalidates both a mapping
of single stage translation and a mapping of nested translation with
the same PSCID, but only the former one should be invalidated.

Signed-off-by: Jason Chien <jason.chien@sifive.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20241108110147.11178-1-jason.chien@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>