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_beagle_defconfig b/configs/omap3_beagle_defconfig
index b3c447f..1944c0c 100644
--- a/configs/omap3_beagle_defconfig
+++ b/configs/omap3_beagle_defconfig
@@ -3,7 +3,6 @@
 CONFIG_SYS_TEXT_BASE=0x80100000
 CONFIG_TARGET_OMAP3_BEAGLE=y
 CONFIG_DISTRO_DEFAULTS=y
-CONFIG_SYS_EXTRA_OPTIONS="NAND"
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_VERSION_VARIABLE=y
@@ -37,6 +36,7 @@
 CONFIG_LED_STATUS_GREEN=2
 CONFIG_LED_STATUS_CMD=y
 CONFIG_MMC_OMAP_HS=y
+CONFIG_NAND=y
 CONFIG_SYS_NS16550=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_HCD=y