[MTD] [OneNAND] Get correct density from device ID

Use the higher bits for other purpose.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/include/linux/mtd/onenand_regs.h b/include/linux/mtd/onenand_regs.h
index c46161f..d1b310c 100644
--- a/include/linux/mtd/onenand_regs.h
+++ b/include/linux/mtd/onenand_regs.h
@@ -67,6 +67,7 @@
 /*
  * Device ID Register F001h (R)
  */
+#define ONENAND_DEVICE_DENSITY_MASK	(0xf)
 #define ONENAND_DEVICE_DENSITY_SHIFT	(4)
 #define ONENAND_DEVICE_IS_DDP		(1 << 3)
 #define ONENAND_DEVICE_IS_DEMUX		(1 << 2)