t/io_uring: properly detect numa nodes for passthrough mode

t/io_uring: properly detect numa nodes for passthrough mode

We need to use a different path for the char nodes. With this, my
setup correctly detects the nodes for all devices:

submitter=0, tid=4746, file=/dev/ng0n1, node=6
submitter=1, tid=4747, file=/dev/ng1n1, node=6
submitter=2, tid=4748, file=/dev/ng2n1, node=6
submitter=3, tid=4749, file=/dev/ng3n1, node=6
submitter=4, tid=4750, file=/dev/ng4n1, node=4
submitter=5, tid=4751, file=/dev/ng5n1, node=4
submitter=6, tid=4752, file=/dev/ng6n1, node=4
submitter=7, tid=4753, file=/dev/ng7n1, node=4
submitter=8, tid=4754, file=/dev/ng8n1, node=4
submitter=9, tid=4755, file=/dev/ng9n1, node=4
submitter=10, tid=4756, file=/dev/ng10n1, node=4
submitter=12, tid=4758, file=/dev/ng12n1, node=10
submitter=11, tid=4757, file=/dev/ng11n1, node=4
submitter=13, tid=4759, file=/dev/ng13n1, node=10
[...]

Signed-off-by: Jens Axboe <axboe@kernel.dk>