hw/riscv/riscv-iommu: Fix MSI table size limit

hw/riscv/riscv-iommu: Fix MSI table size limit

The MSI table is not limited to 4k. The only constraint the table has
is that its base address must be aligned to its size, ensuring no
offsets of the table size will overrun when added to the base address
(see "8.5. MSI page tables" of the AIA spec).

Fixes: 0c54acb8243d ("hw/riscv: add RISC-V IOMMU base emulation")
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20250904132723.614507-2-ajones@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>