It looks like the IRQ is asserted on RESET completion and expects a data
chunk from host to deassert the IRQ. I used to test the driver in RPI 4
using iperf3. For some reason I never faced this issue, may be when the
network device is being registered there might be some packet 
transmission which leads to deliver a data chunk so that the IRQ is
deasserted.

If you have IPv6 enabled, the network stack will try to add a link
local IPv6 address to the interface, which means performing a
Duplicate Address Detection. That means sending a few packets.

Try disabling IPv6 if you want to reproduce the problem.

	  Andrew