Convert CONFIG_NAND_OMAP_GPMC et al and CONFIG_NAND_MXC to Kconfig

This converts the following to Kconfig:
   CONFIG_NAND_MXC
   CONFIG_NAND_OMAP_GPMC
   CONFIG_NAND_OMAP_GPMC_PREFETCH
   CONFIG_NAND_OMAP_ELM
   CONFIG_SPL_NAND_AM33XX_BCH
   CONFIG_SPL_NAND_SIMPLE
   CONFIG_SYS_NAND_BUSWIDTH_16BIT

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
[trini: Finish migration of CONFIG_SPL_NAND_SIMPLE, fix some build issues,
        add CONFIG_NAND_MXC so we can do CONFIG_SYS_NAND_BUSWIDTH_16BIT]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/apf27_defconfig b/configs/apf27_defconfig
index e9a1773..378402c 100644
--- a/configs/apf27_defconfig
+++ b/configs/apf27_defconfig
@@ -16,7 +16,6 @@
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y
-CONFIG_CMD_NAND=y
 CONFIG_CMD_NAND_TRIMFFS=y
 CONFIG_CMD_NAND_LOCK_UNLOCK=y
 CONFIG_CMD_DHCP=y
@@ -31,4 +30,7 @@
 CONFIG_CMD_UBI=y
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_MMC_MXC=y
+CONFIG_NAND=y
+CONFIG_NAND_MXC=y
+CONFIG_SYS_NAND_BUSWIDTH_16BIT=y
 CONFIG_OF_LIBFDT=y