When scanning NAND for bad blocks, don't read the whole page, read
only needed OOB bytes instead. Also check the return code of the
nand_read_raw() function. Correctly free the this->bbt array in
case of failure. Tested with Large page NAND.

Fix debugging message.
Signed-off-by: Artem B. Bityuckiy <dedekind@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>