[MTD] OneNAND: Check first or second pages for bad block information

OneNAND records bad block information in the out-of-band area of either the first or second page of a block.  Due to a logic error, only the first page was being checked.

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