xfs: remove unnecessary dstmap in xattr scrubber

Replace bitmap_and with bitmap_intersects in the xattr leaf block
scrubber, since we only care if there's overlap between the used space
bitmap and the free space bitmap.  This means we don't need dstmap any
more, and can thus reduce the memory requirements.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>