configs: phycore-imx8mm_defconfig: Enable LTO

Enable LTO for binary size reduction.

Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
diff --git a/configs/phycore-imx8mm_defconfig b/configs/phycore-imx8mm_defconfig
index ffdb5cc..4a27d15 100644
--- a/configs/phycore-imx8mm_defconfig
+++ b/configs/phycore-imx8mm_defconfig
@@ -21,6 +21,7 @@
 CONFIG_SPL=y
 CONFIG_ENV_OFFSET_REDUND=0x3E0000
 CONFIG_SYS_LOAD_ADDR=0x40480000
+CONFIG_LTO=y
 CONFIG_FIT=y
 CONFIG_FIT_EXTERNAL_OFFSET=0x3000
 CONFIG_SPL_LOAD_FIT=y