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/omap3_logic_defconfig b/configs/omap3_logic_defconfig
index 27c9e21..464a41f 100644
--- a/configs/omap3_logic_defconfig
+++ b/configs/omap3_logic_defconfig
@@ -5,7 +5,6 @@
 CONFIG_TARGET_OMAP3_LOGIC=y
 CONFIG_SPL_STACK_R_ADDR=0x82000000
 CONFIG_DEFAULT_DEVICE_TREE="logicpd-torpedo-37xx-devkit"
-CONFIG_SYS_EXTRA_OPTIONS="NAND"
 # CONFIG_ENV_IS_IN_FAT is not set
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
@@ -36,6 +35,7 @@
 CONFIG_DM_MMC=y
 CONFIG_MMC_OMAP_HS=y
 CONFIG_MMC_OMAP36XX_PINS=y
+CONFIG_NAND=y
 CONFIG_SYS_NS16550=y
 CONFIG_USB=y
 CONFIG_USB_MUSB_GADGET=y