configfs: fold configfs_attach_attr into configfs_lookup

mainline inclusion
from mainline-v5.15-rc1
commit d07f132a
category: bugfix
bugzilla: 187567, https://gitee.com/openeuler/kernel/issues/I5PK1G
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/configfs/dir.c?h=v6.0-rc3&id=d07f132a225c013e59aa77f514ad9211ecab82ee



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

This makes it more clear what gets added to the dcache and prepares
for an additional locking fix.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>