Platform Nand: Set the GPIO for NAND read as input

This patch is from Frank.Shew,fshew@geometrics.com to fix the
following problem:having extremely slow responses with the NAND
due to timeouts on the ready status signal, which eventually
caused the watchdog to time out.
Signed-off-by: Aaron Wu <Aaron.Wu@analog.com>
Signed-off-by: Steven Miao <realmz6@gmail.com>

arch/blackfin/mach-bf537/boards/stamp.c

@@ -455,6 +455,7 @@ static struct platform_device bfin_async_nand_device = {
 static void bfin_plat_nand_init(void)
 {
 	gpio_request(BFIN_NAND_PLAT_READY, "bfin_nand_plat");
+	gpio_direction_input(BFIN_NAND_PLAT_READY);
 }
 #else
 static void bfin_plat_nand_init(void) {}