[XFS] kill the XFS_IMAP_BULKSTAT flag

Just pass down the XFS_IGET_* flags all the way down to xfs_imap instead
of translating them mid-way.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Niv Sardi <xaiki@sgi.com>