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/am335x_baltos_defconfig b/configs/am335x_baltos_defconfig
index 279c28e..492f7b9 100644
--- a/configs/am335x_baltos_defconfig
+++ b/configs/am335x_baltos_defconfig
@@ -65,7 +65,7 @@
 CONFIG_SYS_NAND_PAGE_SIZE=0x800
 CONFIG_SYS_NAND_OOBSIZE=0x40
 CONFIG_SYS_NAND_U_BOOT_LOCATIONS=y
-CONFIG_SYS_NAND_U_BOOT_OFFS=0x00080000
+CONFIG_SYS_NAND_U_BOOT_OFFS=0x80000
 CONFIG_PHY_ADDR_ENABLE=y
 CONFIG_PHY_ATHEROS=y
 CONFIG_PHY_SMSC=y