uboot-mediatek: no compression means IH_COMP_NONE

Treat missing compression node in FIT image as IH_COMP_NONE.
This is implicentely already happening in most places, but for now
was still triggering an annoying warning about initramfs compression
being obsolete despite compression note being absent.
Fix this.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

package/boot/uboot-mediatek/patches/200-cmd-add-imsz-and-imszb.patch

@@ -70,7 +70,7 @@
  {
 --- a/boot/image-fit.c
 +++ b/boot/image-fit.c
-@@ -1995,6 +1995,51 @@ static const char *fit_get_image_type_pr
+@@ -1994,6 +1994,51 @@ static const char *fit_get_image_type_pr
  	return "unknown";
  }