In bhyve arm64, each PCIe interrupt-map entry spans 10 cells because the ARM GIC specifies
#interrupt-cells = 3. On RISC-V, the APLIC uses #interrupt-cells = 2, so each entry spans only 9 cells.
When the PCIe FDT code was originally adapted from arm64, the property allocation size and cell
assignments were reduced to 9 cells per entry, but the loop multiplier retained the 10-cell stride. This
caused the interrupt-map array to be packed incorrectly with gaps, breaking PCI interrupt routing in
guest operating systems.
Correct the loop stride to 9 cells so the interrupt map is properly formed.
Fixes: 7ab1a32cd43c ("bhyve/riscv: Initial import")