xfs: refactor adding recovered intent items to the log

During recovery, every intent that we recover from the log has to be
added to the AIL.  Replace the open-coded addition with a helper.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>