nfsd: fix end_creating() conversion

nfsd: fix end_creating() conversion

Avoid a double-unlock as nfs_create_locked() will have unlocked the
parent and do the dput() manually.

Christian Brauner <brauner@kernel.org> says:

I've taken Neil's proposed fix from [1] and added a commit message.

Fixes: https://lore.kernel.org/202511252132.2c621407-lkp@intel.com [1]
Fixes: bd6ede8a06e8 ("VFS/nfsd/cachefiles/ovl: introduce start_removing() and end_removing()")
Signed-off-by: Neil Brown <neil@brown.name>
Signed-off-by: Christian Brauner <brauner@kernel.org>