ovl: simplify gotos in ovl_rename()

Rather than having three separate goto label: out_unlock, out_dput_old,
and out_dput, make use of that fact that dput() happily accepts a NULL
pointer to reduce this to just one goto label: out_unlock.

olddentry and newdentry are initialised to NULL and only set once a
value dentry is found.  They are then dput() late in the function.

Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/20250716004725.1206467-9-neil@brown.name


Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>