BACKPORT: FROMLIST: ovl: Let helper ovl_i_path_real() return the realinode

Let helper ovl_i_path_real() return the realinode to prepare for
checking non-null realinode in rcu walking path.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

Bug: 315418522
Bug: 296173010
Link: https://lore.kernel.org/lkml/20230516-topografie-gejubelt-dba162b6e735@brauner/T/


Change-Id: I4fed6fe0874215eb381b6879565a98b855916931
Signed-off-by: Pradeep P V K <quic_pragalla@quicinc.com>
Signed-off-by: 朱陆林 <zhululin1@xiaomi.corp-partner.google.com>