xfs: rename _zone variables to _cache

mainline inclusion
from mainline-v5.15-rc4
commit 182696fb
category: bugfix
bugzilla: 188883, https://gitee.com/openeuler/kernel/issues/I76JSK
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=182696fb021fc196e5cbe641565ca40fcf0f885a



--------------------------------

Now that we've gotten rid of the kmem_zone_t typedef, rename the
variables to _cache since that's what they are.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>

Conflicts: fs/xfs/libxfs/xfs_attr_leaf.c
      fs/xfs/libxfs/xfs_inode_fork.c
      fs/xfs/libxfs/xfs_btree.h
      fs/xfs/libxfs/xfs_ialloc_btree.c
      fs/xfs/libxfs/xfs_alloc_btree.c
      fs/xfs/libxfs/xfs_rmap_btree.c
      fs/xfs/libxfs/xfs_refcount_btree.c
      fs/xfs/libxfs/xfs_bmap_btree.c
      fs/xfs/xfs_attr_inactive.c
      fs/xfs/xfs_bmap_item.c
      fs/xfs/xfs_icache.c
      fs/xfs/xfs_icreate_item.c
      fs/xfs/xfs_refcount_item.c
      fs/xfs/xfs_rmap_item.c
      fs/xfs/xfs_super.c
Signed-off-by: Long Li <leo.lilong@huawei.com>