hw/intc: Don't clear pending bits on IRQ lowering

According to PLIC specification (chapter 5), there
is only one case, when interrupt is claimed. Fix
PLIC controller to match this behavior.

Signed-off-by: Sergey Makarov <s.makarov@syntacore.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240918140229.124329-3-s.makarov@syntacore.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
diff --git a/hw/intc/sifive_plic.c b/hw/intc/sifive_plic.c
index 8de3a65..ed74490 100644
--- a/hw/intc/sifive_plic.c
+++ b/hw/intc/sifive_plic.c
@@ -354,8 +354,10 @@
 {
     SiFivePLICState *s = opaque;
 
-    sifive_plic_set_pending(s, irq, level > 0);
-    sifive_plic_update(s);
+    if (level > 0) {
+        sifive_plic_set_pending(s, irq, true);
+        sifive_plic_update(s);
+    }
 }
 
 static void sifive_plic_realize(DeviceState *dev, Error **errp)