NAND: Subpage shift for ecc_steps equal to 16

This was originally part of Thomas Gleixner's patch for
adding support for 4KiB pages.
This is not part of the U-Boot NAND driver so updating the
driver with this to sync up with the kernel NAND driver.

Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>

drivers/mtd/nand/nand_base.c

@@ -2895,6 +2895,7 @@ int nand_scan_tail(struct mtd_info *mtd)
 			break;
 		case 4:
 		case 8:
+		case 16:
 			mtd->subpage_sft = 2;
 			break;
 		}