In arm_gicv2m_alloc_msi(), if we found a suitable irq range, leave the loop
before we increase irq again, or we'd end up choosing an irq, and then
really using the next one, even if it's not available.
Also in the inner loop, correct the end check so that we check every irq,
even the last one.
This makes the msk(4) adapter able to use MSI on Softiron Overdrive 1000.