udoo_neo: Select LTO

u-boot.img has grown in such a way that it overwrites the
environment region.

Select CONFIG_LTO to help reducing the U-Boot binary size
and add a build-time size check to avoid U-Boot to overlap
the environment region.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
diff --git a/configs/udoo_neo_defconfig b/configs/udoo_neo_defconfig
index 9f9ad0a..97e3b37 100644
--- a/configs/udoo_neo_defconfig
+++ b/configs/udoo_neo_defconfig
@@ -19,6 +19,9 @@
 CONFIG_SPL=y
 CONFIG_SPL_LIBDISK_SUPPORT=y
 # CONFIG_CMD_BMODE is not set
+CONFIG_LTO=y
+CONFIG_HAS_BOARD_SIZE_LIMIT=y
+CONFIG_BOARD_SIZE_LIMIT=523264
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_BOOTCOMMAND="run findfdt; run distro_bootcmd"
 CONFIG_SYS_PBSIZE=532