netfs: Fix ref leak on inserted extra subreq in write retry

netfs: Fix ref leak on inserted extra subreq in write retry

The write-retry algorithm will insert extra subrequests into the list if it
can't get sufficient capacity to split the range that needs to be retried
into the sequence of subrequests it currently has (for instance, if the
cifs credit pool has fewer credits available than it did when the range was
originally divided).

However, the allocator furnishes each new subreq with 2 refs and then
another is added for resubmission, causing one to be leaked.

Fix this by replacing the ref-getting line with a neutral trace line.

Fixes: 288ace2f57c9 ("netfs: New writeback implementation")
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/20250701163852.2171681-6-dhowells@redhat.com
Tested-by: Steve French <sfrench@samba.org>
Reviewed-by: Paulo Alcantara <pc@manguebit.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>