xfs_db: fix finobt record decoding when sparse inodes enabled

xfs_db: fix finobt record decoding when sparse inodes enabled

Use the sparse inobt record field decoder (inobt_spcrc_hfld) to decode
finobt records when sparse inodes are enabled.  Otherwise, xfs_db
prints out bogus things like:

recs[1] = [startino,freecount,free]
1:[214720,16429,0xfffffffffff80000]

There can never be 16429 records in an inode btree record; instead it
should print:

recs[1] = [startino,holemask,count,freecount,free]
1:[214720,0,64,45,0xfffffffffff80000]

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>