[MTD] [NAND] fsl_elbc_nand: ecclayout cleanups

This patch deletes oobavail assignments, they're calculated by the nand
core code in nand_scan_tail, plus current oobavail values are wrong for
the LP NANDs.

Also remove mtd->ecclayout and mtd->oobavail assignments, mtd core
handles this all by itself.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>