xfs: remove variables that serve no purpose in xfs_alloc_ag_vextent_exact()

	xfs_agblock_t	tbno;	/* start block of trimmed extent */

	xfs_extlen_t	tlen;	/* length of trimmed extent */

	xfs_agblock_t	tend;	/* end block of trimmed extent */

	xfs_agblock_t	end;	/* end of allocated extent */

	int		i;	/* success/failure of operation */

	xfs_extlen_t	rlen;	/* length of returned extent */

	ASSERT(args->alignment == 1);

	 *

	 * Fix the length according to mod and prod if given.

	 */

	end = XFS_AGBLOCK_MIN(tend, args->agbno + args->maxlen);

	args->len = end - args->agbno;

	args->len = XFS_AGBLOCK_MIN(tend, args->agbno + args->maxlen)

						- args->agbno;

	xfs_alloc_fix_len(args);

	if (!xfs_alloc_fix_minleft(args))

		goto not_found;

	rlen = args->len;

	ASSERT(args->agbno + rlen <= tend);

	end = args->agbno + rlen;

	ASSERT(args->agbno + args->len <= tend);

	/*

	 * We are allocating agbno for rlen [agbno .. end]

	 * We are allocating agbno for args->len

	 * Allocate/initialize a cursor for the by-size btree.

	 */

	cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,