mtd: fsmc: Support of 224-bytes OOB area length

The current patch is required to support EVALSPEAR1340CPU
Revision 2 where a new (ONFI compliant) MT29F16G08 NAND
flash from Micron is present.

This NAND flash device defines a OOB area which is
224 bytes long (oobsize).

Signed-off-by: Armando Visconti <armando.visconti@st.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>