Restore "u-boot: Relax KCFLAGS warnings for GCC 15"

This reverts commit d0b41d26f87389b1c8dded21777e20739130aa1f.

Reason for revert: unbreak the build. See also
https://fusion2.corp.google.com/invocations/67c2e49b-452f-4b82-ae43-6be41ccb8728/targets/gbmc%2Ffirmware-build%2Fpresubmit/log

Tested: this is a revert
Google-Bug-Id: 558753346
Change-Id: I4223ece3b5ddfeca7d4f31068f280f96e1da255d
Signed-off-by: Bart Van Assche <bvanassche@google.com>

dynamic-layers/aspeed-layer/recipes-bsp/u-boot/u-boot-aspeed-sdk_%.bbappend

diff --git a/dynamic-layers/aspeed-layer/recipes-bsp/u-boot/u-boot-aspeed-sdk_%.bbappend b/dynamic-layers/aspeed-layer/recipes-bsp/u-boot/u-boot-aspeed-sdk_%.bbappend
index fae379b..daa5d32 100644
--- a/dynamic-layers/aspeed-layer/recipes-bsp/u-boot/u-boot-aspeed-sdk_%.bbappend
+++ b/dynamic-layers/aspeed-layer/recipes-bsp/u-boot/u-boot-aspeed-sdk_%.bbappend
@@ -16,3 +16,10 @@
 SRC_URI:append:gbmc:aspeed-g7 = " \
     file://0001-u-boot-adjust-memory-layout-for-ast2700.patch \
 "
+
+EXTRA_OEMAKE:append:gbmc = " KCFLAGS='-Wno-error=int-conversion \
+  -Wno-error=implicit-function-declaration \
+  -Wno-error=format \
+  -Wno-error=return-type' \
+"
+

dynamic-layers/nuvoton-layer/recipes-bsp/u-boot/u-boot-nuvoton_%.bbappend

diff --git a/dynamic-layers/nuvoton-layer/recipes-bsp/u-boot/u-boot-nuvoton_%.bbappend b/dynamic-layers/nuvoton-layer/recipes-bsp/u-boot/u-boot-nuvoton_%.bbappend
index 0baa0bd..344ea49 100644
--- a/dynamic-layers/nuvoton-layer/recipes-bsp/u-boot/u-boot-nuvoton_%.bbappend
+++ b/dynamic-layers/nuvoton-layer/recipes-bsp/u-boot/u-boot-nuvoton_%.bbappend
@@ -7,3 +7,7 @@
     file://0004-recipe-uboot-WA-to-disable-GFX-module.patch \
     file://0005-misc-npcm_host_intf-Disable-pending-KCS-BPC-interrup.patch \
   "
+EXTRA_OEMAKE:append:gbmc = " KCFLAGS='-Wno-error=int-conversion \
+  -Wno-error=implicit-function-declaration \
+  -Wno-error=format' \
+"