mtd: gpmi: only scan two chips for imx6

We cannot scan two chips for imx23 and imx28:
  imx23: the Ready-Busy1 line is not connected for some board.
  imx28: we do not set the pinctrl for Ready-Busy1

So we only scan two chips for imx6.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/gpmi-nand/gpmi-nand.c

@@ -1674,7 +1674,7 @@ static int gpmi_nfc_init(struct gpmi_nand_data *this)
 	if (ret)
 		goto err_out;
 
-	ret = nand_scan_ident(mtd, 2, NULL);
+	ret = nand_scan_ident(mtd, GPMI_IS_MX6Q(this) ? 2 : 1, NULL);
 	if (ret)
 		goto err_out;