Convert CONFIG_NAND to Kconfig

This converts the following to Kconfig:
   CONFIG_NAND

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Sync up a few more, add imply's]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/B4860QDS_NAND_defconfig b/configs/B4860QDS_NAND_defconfig
index 4e30b98..6d03740 100644
--- a/configs/B4860QDS_NAND_defconfig
+++ b/configs/B4860QDS_NAND_defconfig
@@ -10,7 +10,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL,NAND"
+CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL"
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_BOOTDELAY=10
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
@@ -31,6 +31,7 @@
 CONFIG_FSL_CAAM=y
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y
+CONFIG_NAND=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_SST=y
 CONFIG_PHYLIB=y