xfs: use new extent lookup helpers in xfs_bmapi_read

	struct xfs_mount	*mp = ip->i_mount;

	struct xfs_ifork	*ifp;

	struct xfs_bmbt_irec	got;

	struct xfs_bmbt_irec	prev;

	xfs_fileoff_t		obno;

	xfs_fileoff_t		end;

	xfs_extnum_t		lastx;

	xfs_extnum_t		idx;

	int			error;

	int			eof;

	bool			eof = false;

	int			n = 0;

	int			whichfork = xfs_bmapi_whichfork(flags);

			return error;

	}

	xfs_bmap_search_extents(ip, bno, whichfork, &eof, &lastx, &got, &prev);

	if (!xfs_iext_lookup_extent(ip, ifp, bno, &idx, &got))

		eof = true;

	end = bno + len;

	obno = bno;

			break;

		/* Else go on to the next record. */

		if (++lastx < xfs_iext_count(ifp))

			xfs_bmbt_get_all(xfs_iext_get_ext(ifp, lastx), &got);

		else

			eof = 1;

		if (!xfs_iext_get_extent(ifp, ++idx, &got))

			eof = true;

	}

	*nmap = n;

	return 0;