mtd: nand: Introduce CONFIG_SYS_NAND_BUSWIDTH_16BIT

Introduce CONFIG_SYS_NAND_BUSWIDTH_16BIT option so that other NAND controller
drivers could use it when a 16-bit NAND is deployed.

drivers/mtd/nand/ndfc has CONFIG_SYS_NDFC_16BIT, so just rename it, so that
other NAND drivers could reuse the same symbol.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Scott Wood <scottwood@freescale.com>
Reviewed-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>

README

@@ -3755,9 +3755,12 @@ Low Level (hardware related) configuration options:
 - CONFIG_SYS_SRIOn_MEM_SIZE:
 		Size of SRIO port 'n' memory region
 
-- CONFIG_SYS_NDFC_16
-		Defined to tell the NDFC that the NAND chip is using a
-		16 bit bus.
+- CONFIG_SYS_NAND_BUSWIDTH_16BIT
+		Defined to tell the NAND controller that the NAND chip is using
+		a 16 bit bus.
+		Not all NAND drivers use this symbol.
+		Example of driver that uses it:
+		- drivers/mtd/nand/ndfc.c
 
 - CONFIG_SYS_NDFC_EBC0_CFG
 		Sets the EBC0_CFG register for the NDFC. If not defined

drivers/mtd/nand/ndfc.c

@@ -156,7 +156,7 @@ static uint8_t ndfc_read_byte(struct mtd_info *mtd)
 
 	struct nand_chip *chip = mtd->priv;
 
-#ifdef CONFIG_SYS_NDFC_16BIT
+#ifdef CONFIG_SYS_NAND_BUSWIDTH_16BIT
 	return (uint8_t) readw(chip->IO_ADDR_R);
 #else
 	return readb(chip->IO_ADDR_R);
@@ -218,7 +218,7 @@ int board_nand_init(struct nand_chip *nand)
 	nand->ecc.bytes = 3;
 	nand->select_chip = ndfc_select_chip;
 
-#ifdef CONFIG_SYS_NDFC_16BIT
+#ifdef CONFIG_SYS_NAND_BUSWIDTH_16BIT
 	nand->options |= NAND_BUSWIDTH_16;
 #endif