hw/intc: sifive_plic: fix hard-coded max priority level

The maximum priority level is hard-coded when writing to interrupt
priority register. However, when writing to priority threshold register,
the maximum priority level is from num_priorities Property which is
configured by platform.

Also change interrupt priority register to use num_priorities Property
in maximum priority level.

Signed-off-by: Emmanuel Blot <emmanuel.blot@sifive.com>
Signed-off-by: Jim Shu <jim.shu@sifive.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20221003041440.2320-2-jim.shu@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/intc/sifive_plic.c

@@ -180,8 +180,10 @@ static void sifive_plic_write(void *opaque, hwaddr addr, uint64_t value,
     if (addr_between(addr, plic->priority_base, plic->num_sources << 2)) {
         uint32_t irq = ((addr - plic->priority_base) >> 2) + 1;
 
-        plic->source_priority[irq] = value & 7;
-        sifive_plic_update(plic);
+        if (value <= plic->num_priorities) {
+            plic->source_priority[irq] = value;
+            sifive_plic_update(plic);
+        }
     } else if (addr_between(addr, plic->pending_base,
                             plic->num_sources >> 3)) {
         qemu_log_mask(LOG_GUEST_ERROR,