ramips: use lzma-loader on JCG Q20

Fixes the LZMA uncompression issue on JCG Q20.

Signed-off-by: Du Cai <[email protected]>

target/linux/ramips/image/mt7621.mk

@@ -1133,6 +1133,7 @@ TARGET_DEVICES += jcg_jhr-ac876m
 
 define Device/jcg_q20
   $(Device/dsa-migration)
+  $(Device/uimage-lzma-loader)
   BLOCKSIZE := 128k
   PAGESIZE := 2048
   UBINIZE_OPTS := -E 5