Delay floppy READ ID completion

Insert a floppy image like this one in Windows 98 SE. Just clicking the A: drive in My Computer causes repeated stalls of ~7.5 seconds.

This happens because exec_read_id raises IRQ6 synchronously before Windows has set its interrupt-wait flag. The handler rejects the interrupt, leaving the result unread until the driver times out and resets the controller. This happens with JIT disabled too.

Delaying completion by just 1 ms solves it, but QEMU uses 20 ms.

You can check the slop86 fix.