mtd: nand: omap: read nand using register address

Now that gpmc-nand registers are available in driver, use it
to read nand data.

"65b97cf6  mtd: nand: omap2: handle nand on gpmc" modified all
other instances. After initial versions of that patch, a new
change added reading nand data using gpmc exposed function.
In the final version this change was not taken care.
Signed-off-by: Afzal Mohammed <afzal@ti.com>

drivers/mtd/nand/omap2.c

@@ -996,7 +996,7 @@ static int omap_wait(struct mtd_info *mtd, struct nand_chip *chip)
 		cond_resched();
 	}
 
-	status = gpmc_nand_read(info->gpmc_cs, GPMC_NAND_DATA);
+	status = readb(info->reg.gpmc_nand_data);
 	return status;
 }