atmel_nand: don't require CONFIG_SYS_NAND_ENABLE_PIN

If NCE is hooked up to NCS3, we don't need to (and can't)
explicitly set the state of the NCE pin. Instead, the
controller asserts it automatically as part of a
command/data access. Only "CE don't care"-type NAND chips
can be used in this manner.

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Reinhard Meyer <u-boot@emk-elektronik.de>

drivers/mtd/nand/atmel_nand.c

@@ -249,8 +249,10 @@ static void at91_nand_hwcontrol(struct mtd_info *mtd,
 		if (ctrl & NAND_ALE)
 			IO_ADDR_W |= CONFIG_SYS_NAND_MASK_ALE;
 
+#ifdef CONFIG_SYS_NAND_ENABLE_PIN
 		at91_set_gpio_value(CONFIG_SYS_NAND_ENABLE_PIN,
 				    !(ctrl & NAND_NCE));
+#endif
 		this->IO_ADDR_W = (void *) IO_ADDR_W;
 	}