[MTD] NAND: Fix bad block table scan for small page devices

Scan 1st and 2nd pages of SP devices for BB marker by default.
Fix more then one page scanning in create_bbt.c.

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