Convert CONFIG_SYS_NAND_U_BOOT_LOCATIONS et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_NAND_U_BOOT_LOCATIONS
   CONFIG_SYS_NAND_U_BOOT_OFFS

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/gwventana_nand_defconfig b/configs/gwventana_nand_defconfig
index ff5001e..8ff8ab4 100644
--- a/configs/gwventana_nand_defconfig
+++ b/configs/gwventana_nand_defconfig
@@ -100,6 +100,8 @@
 CONFIG_MTD_RAW_NAND=y
 CONFIG_NAND_MXS=y
 CONFIG_NAND_MXS_DT=y
+CONFIG_SYS_NAND_U_BOOT_LOCATIONS=y
+CONFIG_SYS_NAND_U_BOOT_OFFS=0xe00000
 CONFIG_PHYLIB=y
 CONFIG_DM_ETH=y
 CONFIG_DM_MDIO=y