ramips: fix booting on Samknows SK-WB8

This fixes a well known "LZMA ERROR 1" error, reported previously on
numerous of similar devices.

Fixes: #9824
Signed-off-by: Piotr Dymacz <[email protected]>

target/linux/ramips/image/mt7621.mk

@@ -1461,6 +1461,7 @@ TARGET_DEVICES += renkforce_ws-wn530hp3-a
 
 define Device/samknows_whitebox-v8
   $(Device/dsa-migration)
+  $(Device/uimage-lzma-loader)
   IMAGE_SIZE := 16064k
   DEVICE_VENDOR := SamKnows
   DEVICE_MODEL := Whitebox 8