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/imx6q_logic_defconfig b/configs/imx6q_logic_defconfig
index 526a9f3..17875e9 100644
--- a/configs/imx6q_logic_defconfig
+++ b/configs/imx6q_logic_defconfig
@@ -32,6 +32,7 @@
 # CONFIG_BLK is not set
 CONFIG_SYS_I2C_MXC=y
 # CONFIG_DM_MMC_OPS is not set
+CONFIG_NAND=y
 CONFIG_NAND_MXS=y
 CONFIG_PHYLIB=y
 CONFIG_FEC_MXC=y