mtd: nand: Fix NAND_USE_BOUNCE_BUFFER flag conflict

Commit 66507c7b ("mtd: nand: Add support to use nand_base
poi databuf as bounce buffer") added a flag NAND_USE_BOUNCE_BUFFER
using the same bit value as the existing NAND_BUSWIDTH_AUTO.

Cc: Kamal Dasu <kdasu.kdev@gmail.com>
Fixes: 66507c7b

 ("mtd: nand: Add support to use nand_base
	poi databuf as bounce buffer")
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>