lib/decompress_unlz4.c: always set an error return code on failures

"ret", being set to -1 early on, gets cleared by the first invocation of
lz4_decompress()/lz4_decompress_unknownoutputsize(), and hence subsequent
failures wouldn't be noticed by the caller without setting it back to -1
right after those calls.
Reported-by: Matthew Daley <mattjd@gmail.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Kyungsik Lee <kyungsik.lee@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/decompress_unlz4.c

@@ -141,6 +141,7 @@ STATIC inline int INIT unlz4(u8 *input, int in_len,
 			goto exit_2;
 		}
 
+		ret = -1;
 		if (flush && flush(outp, dest_len) != dest_len)
 			goto exit_2;
 		if (output)