mtd: nand: add support for Samsung K9LCG08U0B

Assume that:
          tmp = ((extid >> 2) & 0x04) | (extid & 0x03));

From the K9LCG08U0B's datasheet, we know that:
  the oob size is 640 when tmp is 6;
  the oob size is 1024 when tmp is 7;

Signed-off-by: Huang Shijie <b32955@freescale.com>
[Brian: fixed compile issue]
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/nand_base.c

@@ -3285,9 +3285,12 @@ static void nand_decode_ext_id(struct mtd_info *mtd, struct nand_chip *chip,
 			mtd->oobsize = 512;
 			break;
 		case 6:
-		default: /* Other cases are "reserved" (unknown) */
 			mtd->oobsize = 640;
 			break;
+		case 7:
+		default: /* Other cases are "reserved" (unknown) */
+			mtd->oobsize = 1024;
+			break;
 		}
 		extid >>= 2;
 		/* Calc blocksize */