ANDROID: overlayfs: Fix a regression in commit b24be4ac

Fixes a regression in commit b24be4ac
("ovl: modify ovl_permission() to do checks on two inodes") by
replacing a call to revert_creds with internal ovl_revert_creds.

Signed-off-by: Robin Peng <robinpeng@google.com>
Acked-by: Mark Salyzyn <salyzyn@google.com>
Bug: 137827669
Bug: 137827828
Change-Id: I7b542e23554d30347944626dd2d6c48e081e59d9