net: netdevsim: try to close UDP port harness races

[ Upstream commit 50bf398e1ceacb9a7f85bd3bdca065ebe5cb6159 ]

syzbot discovered that we remove the debugfs files after we free
the netdev. Try to clean up the relevant dir while the device
is still around.

Reported-by:  <syzbot+2e5de9e3ab986b71d2bf@syzkaller.appspotmail.com>
Fixes: 424be63a ("netdevsim: add UDP tunnel port offload support")
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Link: https://patch.msgid.link/20250122224503.762705-1-kuba@kernel.org


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