xfs: refactor xfs_iget calls from log intent recovery

Hoist the code from xfs_bui_item_recover that igets an inode and marks
it as being part of log intent recovery.  The next patch will want a
common function.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>