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/tricorder_flash_defconfig b/configs/tricorder_flash_defconfig
index 863135d..022e951 100644
--- a/configs/tricorder_flash_defconfig
+++ b/configs/tricorder_flash_defconfig
@@ -9,6 +9,9 @@
 CONFIG_SYS_EXTRA_OPTIONS="FLASHCARD"
 CONFIG_BOOTDELAY=0
 CONFIG_SILENT_CONSOLE=y
+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_EEPROM=y
@@ -41,7 +44,6 @@
 CONFIG_MMC_OMAP_HS=y
 CONFIG_MTD=y
 CONFIG_MTD_RAW_NAND=y
-CONFIG_SPL_NAND_SIMPLE=y
 CONFIG_CONS_INDEX=3
 CONFIG_SYS_NS16550=y
 CONFIG_BCH=y