x86: allow non gzipped images

The previous image generation code would always gzipped images.

This patch changes the behaviour and only compresses images when
selected in menuconfig.

Signed-off-by: Paul Spooren <mail@aparcar.org>

target/linux/x86/image/Makefile

@@ -95,10 +95,15 @@ endef
 DEVICE_VARS += GRUB2_VARIANT
 define Device/Default
   ARTIFACT/image.iso := grub-config iso | iso
-  IMAGES := combined.img.gz
+  IMAGE/combined.img := append-rootfs | pad-extra 128k | grub-config pc | combined | grub-install
   IMAGE/combined.img.gz := append-rootfs | pad-extra 128k | grub-config pc | combined | grub-install | gzip
   IMAGE/combined.vdi := append-rootfs | pad-extra 128k | grub-config pc | combined | grub-install | qemu-image vdi
   IMAGE/combined.vmdk := append-rootfs | pad-extra 128k | grub-config pc | combined | grub-install | qemu-image vmdk
+  ifeq ($(CONFIG_TARGET_IMAGES_GZIP),y)
+    IMAGES := combined.img.gz
+  else
+    IMAGES := combined.img
+  endif
   KERNEL := kernel-bin
   KERNEL_INSTALL := 1
   KERNEL_NAME := bzImage