xfs: add a block to inode count converter

Add new helpers to convert units of fs blocks into inodes, and AG blocks
into AG inodes, respectively.  Convert all the open-coded conversions
and XFS_OFFBNO_TO_AGINO(, , 0) calls to use them, as appropriate.  The
OFFBNO_TO_AGINO macro is retained for xfs_repair.

Signed-off-by: Darrick J. Wong <[email protected]>
Reviewed-by: Brian Foster <[email protected]>
8 files changed