In the section "4.7 Precise effects on interrupt-pending bits"
of the RISC-V AIA specification defines that:
"If the source mode is Level1 or Level0 and the interrupt domain
is configured in MSI delivery mode (domaincfg.DM = 1):
The pending bit is cleared whenever the rectified input value is
low, when the interrupt is forwarded by MSI, or by a relevant
write to an in_clrip register or to clripnum."
Update the riscv_aplic_set_pending() to match the spec.
Fixes: bf31cf06eb ("hw/intc/riscv_aplic: Fix setipnum_le write emulation for APLIC
MSI-mode")