Convert CONFIG_SPL_NAND_DRIVERS et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_NAND_DRIVERS
   CONFIG_SPL_NAND_ECC
   CONFIG_SPL_NAND_SIMPLE

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/omap3_ha_defconfig b/configs/omap3_ha_defconfig
index 93703e8..ce5a44f 100644
--- a/configs/omap3_ha_defconfig
+++ b/configs/omap3_ha_defconfig
@@ -9,6 +9,9 @@
 CONFIG_SYS_EXTRA_OPTIONS="SYS_BOARD_OMAP3_HA"
 CONFIG_BOOTDELAY=3
 # CONFIG_SPL_FS_EXT4 is not set
+CONFIG_SPL_NAND_DRIVERS=y
+CONFIG_SPL_NAND_ECC=y
+CONFIG_SPL_NAND_SIMPLE=y
 CONFIG_HUSH_PARSER=y
 # CONFIG_CMD_IMI is not set
 # CONFIG_CMD_FLASH is not set
@@ -32,7 +35,6 @@
 CONFIG_MTD=y
 CONFIG_MTD_RAW_NAND=y
 CONFIG_SYS_NAND_BUSWIDTH_16BIT=y
-CONFIG_SPL_NAND_SIMPLE=y
 CONFIG_CONS_INDEX=3
 CONFIG_SYS_NS16550=y
 CONFIG_SPI=y