uboot-bcm4908: fix build with GCC14

A lot of warnings were treated as errors after the default compiler
switched to GCC14. It's hard to fix them one by one, and this u-boot
is not maintained by upstream, so let's just silence these warnings.

Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/18833
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

include/u-boot.mk

@@ -78,6 +78,7 @@ UBOOT_MAKE_FLAGS = \
 	PKG_CONFIG_PATH="$(STAGING_DIR_HOST)/lib/pkgconfig" \
 	PKG_CONFIG_LIBDIR="$(STAGING_DIR_HOST)/lib/pkgconfig" \
 	PKG_CONFIG_EXTRAARGS="--static" \
+	$(if $(KBUILD_CFLAGS),KCFLAGS="$(KBUILD_CFLAGS)") \
 	$(if $(findstring c,$(OPENWRT_VERBOSE)),V=1,V='')
 
 define Build/U-Boot/Target

package/boot/uboot-bcm4908/Makefile

@@ -32,6 +32,12 @@ define U-Boot/bcm4912
   SOC:=bcm4912
 endef
 
+KBUILD_CFLAGS := \
+	-Wno-error=implicit-function-declaration \
+	-Wno-error=implicit-int \
+	-Wno-error=incompatible-pointer-types \
+	-Wno-error=int-conversion
+
 UBOOT_TARGETS := \
 	bcm4908 \
 	bcm4912