Convert CONFIG_NAND_ATMEL to Kconfig

This converts the following to Kconfig:
   CONFIG_NAND_ATMEL

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/wb45n_defconfig b/configs/wb45n_defconfig
index 6dc7c2e..f52d46e 100644
--- a/configs/wb45n_defconfig
+++ b/configs/wb45n_defconfig
@@ -23,5 +23,7 @@
 CONFIG_CMD_MII=y
 CONFIG_CMD_PING=y
 CONFIG_ENV_IS_IN_NAND=y
+CONFIG_NAND=y
+CONFIG_NAND_ATMEL=y
 CONFIG_LZMA=y
 CONFIG_OF_LIBFDT=y