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/devkit8000_defconfig b/configs/devkit8000_defconfig
index 2a32e54..1c067fd 100644
--- a/configs/devkit8000_defconfig
+++ b/configs/devkit8000_defconfig
@@ -46,5 +46,7 @@
 CONFIG_SYS_NAND_PAGE_SIZE=0x800
 CONFIG_SYS_NAND_OOBSIZE=0x40
 CONFIG_SYS_NAND_BUSWIDTH_16BIT=y
+CONFIG_SYS_NAND_U_BOOT_LOCATIONS=y
+CONFIG_SYS_NAND_U_BOOT_OFFS=0x80000
 CONFIG_CONS_INDEX=3
 CONFIG_OF_LIBFDT=y