net: drv: netdevsim: don't napi_complete() from netpoll

In the Linux kernel, the following vulnerability has been resolved:

net: drv: netdevsim: don't napi_complete() from netpoll

netdevsim supports netpoll. Make sure we don't call napi_complete() from it, since it may not be scheduled. Breno reports hitting a warning in napi_complete_done():

WARNING: CPU: 14 PID: 104 at net/core/dev.c:6592 napi_complete_done+0x2cc/0x560 __napi_poll+0x2d8/0x3a0 handle_softirqs+0x1fe/0x710

This is presumably after netpoll stole the SCHED bit prematurely.