xfs: fix a use after free in xfs_defer_finish_recovery

dfp will be freed by ->recover_work and thus the tracepoint in case
of an error can lead to a use after free.

Store the defer ops in a local variable to avoid that.

Fixes: 7f2f7531 ("xfs: store an ops pointer in struct xfs_defer_pending")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>