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.

Reported-by: Breno Leitao <leitao@debian.org>
Fixes: 3762ec05 ("netdevsim: add NAPI support")
Tested-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20250611174643.2769263-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>