uboot-mediatek: mark all packages as hidden

They are enabled by selecting devices. Fixes build errors when enabling extra
devices without creating a new config from scratch.

Signed-off-by: Felix Fietkau <[email protected]>

package/boot/uboot-mediatek/Makefile

@@ -34,6 +34,7 @@ endif
 define U-Boot/Default
   BUILD_TARGET:=mediatek
   UBOOT_IMAGE:=u-boot-mtk.bin
+  HIDDEN:=1
 endef
 
 define U-Boot/mt7620_rfb