Convert CONFIG_SPL_NAND_BASE et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_NAND_BASE
   CONFIG_SPL_NAND_IDENT

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/omap3_logic_defconfig b/configs/omap3_logic_defconfig
index 4ca486a..755d86d 100644
--- a/configs/omap3_logic_defconfig
+++ b/configs/omap3_logic_defconfig
@@ -28,6 +28,7 @@
 CONFIG_SPL_NAND_DRIVERS=y
 CONFIG_SPL_NAND_ECC=y
 CONFIG_SPL_NAND_SIMPLE=y
+CONFIG_SPL_NAND_BASE=y
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SYS_PROMPT="OMAP Logic # "
 # CONFIG_CMD_IMI is not set