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/sama5d3_xplained_mmc_defconfig b/configs/sama5d3_xplained_mmc_defconfig
index 11ca60f..450ebe0 100644
--- a/configs/sama5d3_xplained_mmc_defconfig
+++ b/configs/sama5d3_xplained_mmc_defconfig
@@ -71,6 +71,8 @@
 CONFIG_ATMEL_NAND_HW_PMECC=y
 CONFIG_PMECC_CAP=4
 CONFIG_SYS_NAND_ONFI_DETECTION=y
+CONFIG_SYS_NAND_U_BOOT_LOCATIONS=y
+CONFIG_SYS_NAND_U_BOOT_OFFS=0x40000
 CONFIG_DM_ETH=y
 CONFIG_MACB=y
 CONFIG_PINCTRL=y