i2c: Allow irq to be cleared

src/main/scala/devices/i2c/I2C.scala

@@ -488,16 +488,16 @@ trait HasI2CModuleContents extends MultiIOModule with HasRegMap {
 
   // hack: b/c the same register offset is used to write cmd and read status
   val nextCmd = Wire(UInt(8.W))
-  nextCmd := cmd.asUInt
   cmd := (new CommandBundle).fromBits(nextCmd)
+  nextCmd := cmd.asUInt & 0xFE.U  // clear IRQ_ACK bit (essentially 1 cycle pulse b/c it is overwritten by regmap below)
 
+  // Note: This wins over the regmap update of nextCmd (even if something tries to write them to 1, these values take priority).
   when (cmdAck || arbLost) {
     cmd.start := false.B    // clear command bits when done
     cmd.stop  := false.B    // or when aribitration lost
     cmd.read  := false.B
     cmd.write := false.B
   }
-  cmd.irqAck  := false.B    // clear IRQ_ACK bit (essentially 1 cycle pulse b/c it is overwritten by regmap below)
 
   status.receivedAck := receivedAck
   when (stopCond) {