passthrough_ll: pass correct errno to fuse_reply_err()

passthrough_ll: pass correct errno to fuse_reply_err()

fuse_reply_err() expects the error code, not its negative.

Upstreamed from https://www.redhat.com/archives/virtio-fs/2020-January/msg00000.html. Original commit message:

lo_copy_file_range() passes -errno to fuse_reply_err() and then fuse_reply_err()
changes it to errno again, so that subsequent fuse_send_reply_iov_nofree() catches
the wrong errno.(i.e. reports "fuse: bad error value: ...").

Make fuse_send_reply_iov_nofree() accept the correct -errno by passing errno
directly in lo_copy_file_range().

Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
Reviewed-by: Eryu Guan <eguan@linux.alibaba.com>
Co-authored-by: Xiao Yang <ice_yangxiao@163.com>