NAND: Add 16bit NAND support for the NDFC

This patch adds support for 16 bit NAND devices attached to the
NDFC on ppc4xx processors. Two config entries were added:

  CONFIG_SYS_NDFC_16        - Setting this tells the NDFC that a
			      16 bit device is attached.
  CONFIG_SYS_NDFC_EBC0_CFG  - This is for the External Bus
			      Controller configuration register.

Also, a new ndfc_read_byte() function was added which does not
first convert the data to little endian.

The NAND SPL was also modified to do 16bit bad block testing
when a 16 bit chip is being used.

Signed-off-by: Alex Waterman <awaterman@dawning.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>
diff --git a/nand_spl/nand_boot.c b/nand_spl/nand_boot.c
index 9545a9a..4683c7c 100644
--- a/nand_spl/nand_boot.c
+++ b/nand_spl/nand_boot.c
@@ -122,10 +122,15 @@
 	nand_command(mtd, block, 0, CONFIG_SYS_NAND_BAD_BLOCK_POS, NAND_CMD_READOOB);
 
 	/*
-	 * Read one byte
+	 * Read one byte (or two if it's a 16 bit chip).
 	 */
-	if (readb(this->IO_ADDR_R) != 0xff)
-		return 1;
+	if (this->options & NAND_BUSWIDTH_16) {
+		if (readw(this->IO_ADDR_R) != 0xffff)
+			return 1;
+	} else {
+		if (readb(this->IO_ADDR_R) != 0xff)
+			return 1;
+	}
 
 	return 0;
 }