nfs: Fix nfs_access_get_cached_rcu() sparse error

This patch fixes the following sparse error:
fs/nfs/dir.c:2353:14: error: incompatible types in comparison expression (different address spaces):
fs/nfs/dir.c:2353:14:    struct list_head [noderef] <asn:4> *
fs/nfs/dir.c:2353:14:    struct list_head *

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>