[MTD] OneNAND: Add support for auto-placement of out-of-band data

Enable the use of oob operation mode MTD_OOB_AUTO with OneNAND.
Note that MTD_OOB_RAW is still not supported.

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>